Chronology and typology of
COUSTEAU-GAGNAN regulators
commonly called CG45
marketed from 1946 to 1956
The CG45: or the regulator that had no name.
On July 8, 1943, just four days after the historic first dive in Bandol, Commander Jacques-Yves Cousteau and engineer Émile Gagnan filed the patent for the COUSTEAU-GAGNAN scuba suit.
This innovative device consists of a portable compressed air supply (usually one, two, or three 5-liter aluminum cylinders) and a demand regulator, the central element of the system. This regulator automatically supplies a sufficient quantity of air, expanded to the pressure of the diver's lungs.
Positioned on the back, it ensures optimal breathing comfort, with the diaphragm located at bronchial level. It operates in two stages:
• The first stage of expansion reduces the high pressure to an intermediate pressure of approximately 7 bar.
• The second stage of expansion delivers air at ambient pressure, regardless of depth.
Its ease of use significantly reduces the risk of shortness of breath. Furthermore, its open circuit upon exhalation evacuates bubbles out of the field of vision, ensuring better underwater visibility.
In 1943, the first prototypes of the regulator were rectangular in shape. However, Émile Gagnan quickly realized that a round housing improved performance by better distributing hydrostatic pressure across the diaphragm. Thus, in 1945, the final version, intended for commercialization, adopted a so-called "camembert box" shape.
To launch production, Air Liquide created a subsidiary, SARL LA SPIROTECHNIQUE, founded on May 26, 1946. The first units were marketed in July 1946.
In the early years, the regulators for the COUSTEAU-GAGNAN scuba equipment did not bear a manufacturer's plate. The serial number was stamped either on the front sump (for the very first models) or on the high-pressure body, at least until the end of 1946.
It wasn't until 1947 that the first manufacturer's plate appeared. It bore no name, only the following inscription:
SCAPHANDRE AUTONOME
COUSTEAU-GAGNAN
breveté S.G.D.G
LA SPIROTECHNIQUE
S.A.R.L
Siège social 6 Rue Cognacq Jay, Paris VII
N° 001
It wasn't until 1955, with the arrival of the MISTRAL, that the regulator was truly considered a separate component from the rest of the scuba equipment. Early collectors dubbed it the CG45 (short for COUSTEAU-GAGNAN 1945), a name that has endured to this day, although veterans continue to call it the COUSTEAU-GAGNAN regulator.
Sold from 1946 to 1956, this regulator was only produced in a hookah version during its last two years (1955 and 1956), as the MISTRAL could not be modified for this purpose.
It is, in fact, the brand's only dual-hose regulator that can be converted into a hookah and vice versa. The transformation is relatively simple: simply remove the first stage mechanism, seal the corresponding orifice with a specific plug on the membrane side, then replace the bracket with a low-pressure connector allowing the hookah hose to be connected.
The typology and chronology of GC45
I divided the CG45 into 2 main types :
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The CG45 says archaic mess tin (1946–1949) which is the rarest. It is divided into 3 versions subjected to the expansion of the regulator between 1946 and 1949: l es without a nameplate , the large SARL plates and small SARL plates
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The CG45 says standard and PRO (1950-1956) bowl which is the most common. We see it appear in the 1950s with the PRO version which is used on the new PHOQUE garment, then spread from 1951 on all models with a standard version in addition when switching from LA SPIROTECHIQUE to SA.
THE CG45 WITH ARCHAIC BOWL
The CG45s with their archaic mess kit are distinguished by their thin 22 mm diameter tubing, particularly the exhalation tube, which features a 35° bend.
The explanation is simple: on early scuba suits, the regulator was attached behind the tank. This bend allowed the corrugated exhalation tube to be brought forward without bending it. However, this configuration had several drawbacks: it exposed the regulator to shocks in the event of a fall, and when diving, the corrugated tubes risked being damaged by rocks or sharp metal sheets from wrecks.
Faced with these problems, this arrangement was quickly abandoned in favor of a safer positioning, bringing the regulator between the diver and the tank, thus eliminating the need for an angled exhalation tube.
CG45s without manufacturer's label
The CG45 was marketed without a manufacturer's label during two distinct periods.
In this section, we will focus on the first period, in 1946. At that time, the serial number was initially stamped directly on the exhalation bowl, before being moved to the back, on the high-pressure body, right next to the yoke.
To date, only three examples of this variant have been recorded: serial numbers 150, 516, and 568, making it an extremely rare model. These early regulators were equipped with a FERNEZ-type metal nozzle.
In the gallery, you will find an image of the regulator as it appeared in the 1946 catalog.
Détendeur CG45 archaïque sans plaque constructeur avec numéro de série 568 estampillé à la base du corps HP
Détail de la gamelle du CG45 archaïque sans plaque constructeur.
Vu arrière de la gamelle du CG45 archaïque sans plaque constructeur.
Emplacement du numéro de série sur les CG45 archaïque.
Détail de la courbure d'expiration du CG45 archaïque.
Vue ouverte de la gamelle du CG45 archaïque sans plaque constructeur.
Détail de la gamelle du CG45 archaïque sans plaque constructeur mais avec numéro de série estampillé sur la casserole avant.
Premier ensemble scaphandre autonome COUSTEAU-GAGNAN sortie en Juillet 1946.
Photo extraite du manuel d'utilisation du CG45 de 1946.
THE CG45 WITH LARGE LABEL SARL
In 1947, the first manufacturer's label, known as the large SARL label, appeared. A photo below shows Maurice Fargues, a few minutes before his fateful dive on September 17, 1947, preparing his diving suit equipped with a regulator with a large SARL label.
It is likely that a transition period took place, during which regulators with and without label coexisted. This hypothesis is based on the fact that number 537 was found with a large SARL label, while number 568 does not have a label but bears its serial number stamped on the high-pressure body.
The CG45 with a large SARL label was initially sold with a wide rubber mouthpiece manufactured by GODEL for LA SPIROTECHNIQUE.
An intriguing detail concerns the number 864, which is followed by the letter N. Since this model was mounted as a narguilé, it is possible that this letter stands for narguilé. This regulator is believed to have come from the Arsenal de L'Orient, although the exact reason for this inscription remains unknown. To date, this is the only example of a large SARL label recorded with this particularity, but it is possible that a small series was produced.
The highest known serial number for a CG45 with a large SARL label is 1097, which suggests a production of approximately 550 to 600 units. However, the majority were destroyed when the MISTRAL regulator was released.
After years of research, only 13 examples (numbers 537 - 631- 684 - 763 - 828 - 835 - 864N - 941 - 969 - 970 - 1080 - 1096 - 1097) have been found worldwide, making this model one of the rarest and most coveted by collectors.
Détendeur CG45 grosse plaque SARL portant le numéro de série 1097. Il s'agit d'un des tous derniers exemplaires produits.
Détail de la gamelle du CG45 grosse plaque SARL numéro de série 1097.
Détail de l'embout de LA SPIROTECHNIQUE conçu par GODEL pour le CG45 grosse plaque SARL.
Vue arrière de l'embout caoutchouc avec les indications du fabriquant GODEL.
Voici le plus petit numéro de série de CG45 grosse plaque SARL connu à ce jour. Il porte le numéro 537.
Gamelle du CG45 narguilé numéro de série 864 N. N peut être pour "narguilé"?
Détail de la gamelle arrière du CG45 grosse plaque SARL narguilé numéro de série 864 N.
Démontage d'un CG45 grosse plaque SARL
Photo extraite du manuel d'utilisation du CG45 grosse plaque SARL de 1947.
THE SMALL LABEL CG45 SARL
The Appearance of the CG45 with Small SARL label (1949-1950)
In 1949 (probably as early as the end of 1948), the CG45 with Small SARL label appeared. It was available in two variants:
• Version with an archaic bowl: Still in production, but now equipped with a straight Fernez-type metal mouthpiece, replacing the GODEL rubber mouthpiece.
• Version with a standard bowl (from 1950) in PRO configuration: Specially designed for the new constant-volume garment developed by LA SPIROTECHNIQUE, the PHOQUE suit.
This new bowl is distinguished by enlarged-diameter tubing (from 22 mm to 25 mm), with a now straight exhalation tube. It is equipped with tin-soldered threaded connectors, allowing the PRO nozzle to be fitted and the corrugated hoses to be easily detached from the bowl or nozzle, which remains attached to the hood of the SEAL garment.
Production and Rarity
To date, the lowest serial number recorded for a CG45 with a small SARL label is No. 1137, and the largest is No. 1871, suggesting a production run of approximately 750 to 800 units.
However, only about twenty examples have been found worldwide. Most were scrapped when the MISTRAL regulator was introduced, contributing to their extreme rarity.
Evolution of Plate Mounting
The first units equipped with the small SARL label were mounted vertically, as on the large label models, i.e., with the label positioned perpendicular to the pipes.
It wasn't until around 1950 (probably around serial number 1200) that the orientation changed: the label were now mounted horizontally. This development is explained by the fact that, until 1950, the pipes were aligned horizontally relative to the plane of the regulator.
Intriguing Special Cases
Two atypical regulators have been identified:
• No. 516 (mentioned below)
• No. 583
These discoveries fuel a hypothesis: in 1949, LA SPIROTECHNIQUE sold replacement pans equipped with small SARL labels, engraved at the user's request to preserve the original serial number.
However, this practice seems to have been quickly abandoned (perhaps as early as 1950), in favor of blank pans without a manufacturer's plate, a likely simpler solution for after-sales service.
A still fragmentary history
Unfortunately, LA SPIROTECHNIQUE's archives were almost entirely destroyed during the move from Levallois to Carros. Furthermore, all of the brand's pioneers are no longer with us.
Our current knowledge is based mainly on observations of regulators and the interpretation of rare documents.
Détendeur CG45 petite plaque SARL numéro de série 1137, c'est le plus petit numéro connu à ce jour connu. Remarquez la plaque montée verticalement sur la gamelle.
Détail de la gamelle du CG45 numéro de série 1137.
Détail de la petite plaque SARL numéro de série 1137.
Embout métal de type FERNEZ en T de 1949, c'est l'ancêtre de l'embout D10 qui équipera les MISTRAL standards.
Détendeur petite plaque SARL numéro de série 1219, c'est le plus petit numéro de série connu avec la plaque positionnée horizontalement.
Détail de la plaque du petite plaque SARL numéro 1219.
Détail de la plaque d'un CG45 petite plaque SARL arborant un numéro de série 583. On remarque que les rivets ne sont pas d'origine. En fait, il s'agit probablement du remplacement d'une grosse plaque SARL 583 perdue.
CG45 petite plaque SARL numéro de série 1665 monté avec un embout PRO pour le vêtement à volume constant PHOQUE.
Détail du CG45 petite plaque SARL 1665.
THE CG45 WITH STANDARD BOWL
In 1951, production of the archaic mess tin was definitively discontinued in favor of a new variant, which complemented the standard PRO version. I named it the standard version.
Although visually similar to the PRO version, it differed in the absence of threaded tin fittings on the tubing and in a new straight metal nozzle, shorter than the 1949 Fernez model.
This nozzle was retained after the release of the Mistral regulator in 1955 and later took the name D10 nozzle, in reference to the designation of the standard MISTRAL in the 1962 LA SPIROTECHNIQUE catalog.
THE SMALL LABEL CG45 SA
In 1950, to accommodate the increased production of the COUSTEAU-GAGNAN scuba diving unit, LA SPIROTECHNIQUE changed its legal status from SARL to SA.
This change is confirmed by patent applications available on the INPI website.
At this time, a new small manufacturer's plate appeared, now bearing the words "SA LA SPIROTECHNIQUE."
SCAPHANDRE AUTONOME
COUSTEAU-GAGNAN
breveté S.G.D.G
LA SPIROTECHNIQUE
S.A.
Siège social 6 Rue Cognacq Jay, Paris VII
N° 001
To date I have found CG45s with a small SA label included between serial number N°1960 to N°6194.
Détendeur CG45 à gamelle standard en petite plaque SA avec un embout PROPULS de GODEL.
Détail de la gamelle standard d'un CG45 petite plaque SA.
Détails internes du CG45 petite plaque SA .
Détails de la membrane et du bec de canard du CG45.
Détails du corps haute pression et basse pression du détendeur CG45.
Détail du second étage du détendeur CG45 avec la fourchette en forme de fer à cheval.
Détails du "côté membrane" du premier étage du CG45 après retrait de l'écrou du ressort basse pression.
Détails du "côté membrane" du premier étage du CG45 après retrait de l'écrou et du ressort basse pression.
Détails du "côté clapet HP" du premier étage CG45.
SMALL LABEL CG45 VARIANTS SA
The CG45s with the small SA label are divided into two distinct groups:
First Group (1951-1954)
This group includes regulators whose serial numbers are stamped with thick, coarse numbers, currently covering the serial number range 1960 to 5127.
• The majority of these models are equipped with a yoke, while the hookah versions were produced only on demand for professionals. • Their production extended from 1951 to 1954.
Second group (1955-1956)
This is the last series of CG45s with SA label, produced in 1955 and 1956.
• This series, estimated at around 1,000 units, consists exclusively of CG45s in hookah configuration (simply because the MISTRAL regulator cannot be mounted in narguilé configuration, as it operates with a single regulator stage).
• From 1956 onward, serial numbers were stamped with finer numbers, a format also adopted on the MISTRAL 56s.
This hypothesis is based on my observations in private collections and museums, where the serial numbers recorded range from 5206 to 6194. The latter represents the largest serial number known to date for a CG45 regulator.
Variants of the first group
This group includes two distinct variants:
1. 1951 Series – Serial Numbers Ending with the Letter “M”
A series of at least 230 units, produced in 1951, bears a serial number ending with the letter “M” (confirmed between No. 2542M and No. 2772M).
• The exact meaning of this marking remains unknown, but it likely refers to a series intended for the Navy.
2. 1953 Series – “Reverse Mounted” Plate
In 1953, another series of at least 177 regulators exhibited a unique feature: an inverted manufacturer’s plate, nicknamed “reverse mounted.” This variant is confirmed for serial numbers ranging from No. 4051 to No. 4228.
• Contrary to a factory assembly error, as suggested on some forums, this configuration is intentional.
• If the CG45 is mounted in the traditional manner, with the tubing facing upwards, the plate appears upside down.
• In reality, this series is designed to be rigged with the tubing facing downwards, an arrangement that better protects the rubber hoses, perhaps for use in caving.
• By respecting this orientation, the plate is positioned correctly.
This type of mounting would later be adopted by the Spanish manufacturer NEMROD on the black-label SNARK III regulator.
Détail de la gamelle du CG45 SA numéro de série 2542M. Il s'agit du plus petit numéro de série connu à ce jour.
Détail de la gamelle du CG45 SA numéro de série 2772M.Il s'agit du plus gros numéro de série connu à ce jour.
Détail de la gamelle du CG45 SA dit "plaque montée à l'envers" numéro de série 4051. Il s'agit du plus petit numéro de série connu à ce jour.
Détail de la gamelle du CG45 SA dit "plaque montée à l'envers" numéro de série 4228. Il s'agit du plus gros numéro de série connu à ce jour.
Extrait d'un catalogue de la marque Espagnole NEMROD où l'on voit un SNARK III à étiquette noire avec les tuyaux annelés vers le bas.
Photo du manuel technique du CG45 de 1951.
The second group
As mentioned previously, the narguilé version of the CG45 was produced occasionally and on demand until 1954.
• Its body is identical to that of the yoke version, except that:
• The first-stage mechanism is removed.
• A plug is placed on the membrane side.
• The yoke is replaced by a low-pressure hose connector.
Last production run in 1955-1956: the late narguilé version
In 1955 and 1956, LA SPIROTECHNIQUE produced a final production run, estimated at around 1,000 units, exclusively in the hookah version.
• This series, which I have named the "late narguilé version of the CG-45," is equipped with a manufacturer's label "SA LA SPIROTECHNIQUE."
• Unlike the previous CG45s, whose serial numbers were marked with large numbers, these last units manufactured in 1956 are stamped with small numbers, identical to those used for the MISTRALs marketed from that same year.
A Change of Tooling and the Transition to the MISTRAL
This detail suggests that this late production took place in parallel with the manufacture of the first MISTRALs (Seine).
• Indeed, the MISTRALs produced in 1955, bearing the address “6 RUE COGNACQ JAY PARIS VII,” still used large numbers, like the older CG45s.
• In 1956, a new machine was introduced, abandoning the crude marking of serial numbers.
End of the CG45 in 1957
The CG45 was definitively abandoned in 1957 with the arrival of the CG45-MISTRAL narguilé.
• This new model adopted a US-DIVERS type HP body and a MISTRAL regulator label, thus marking the transition to a new generation of equipment.
Détendeur narguilé CG45 tardif numéro de série 6104.
Détail du raccord du flexible basse pression du narguilé. Sur la version tardive il est coudé.
Détail de la gamelle du CG45 NARGUILÉ tardif. Sur les NARGUILÉS l'étrier est remplacé par un raccord basse pression droit sur les modèles d'avant 1955 ou coudé pour les modèles de 1955 et 1956.
Détail interne du CG45 narguilé tardif. Le mécanisme du premier étage est supprimé et le "coté membrane" et fermé avec un bouchon que l'on démonte avec une clé ergot.
Détail du corps du CG45 NARGUILÉ TARDIF.
Détail de la gamelle du CG45 SA NARGUILÉ numéro de série 6104.
Détail de la gamelle du CG45 SA NARGUILÉ numéro de série 6172. On remarque que les chiffres sont estampillés en petits caractères comme sur les MISTRAL à l'adresse 27 RUE TRÉBOIS LEVALLOIS (SEINE) de 1956.
Détail de la gamelle du CG45 SA NARGUILÉ numéro de série 5206. Il s'agit du plus petit numéro de série connu à ce jour d'un narguilé tardif. Le numéro de série est encore estampillé avec des chiffres grossiers. Ce qui signifie que les premiers exemplaires de la série tardive NARGUILÉ ont étés produit en 1955.
Détail de la gamelle du CG45 NARGUILÉ tardif. Sur les NARGUILÉS l'étrier est remplacé par un raccord basse pression droit sur les modèles jusqu'en 1955 ou coudé pour les modèles de 1955 et 1956.
SPECIAL CASES OF CG45
It's important to put things into context: at the time, scuba diving was still in its infancy, and no standards existed like today. Everything still needed to be organized and structured.
CG45 regulators were frequently modified based on their owner's experience. These modifications could have various purposes: repair, performance improvement, or even customization.
It's also important to understand that the first divers, often former military personnel, attached great importance to their regulator's serial number, a symbol of their seniority and their place in the community. This tradition undoubtedly explains why LA SPIROTECHNIQUE has long displayed the serial number of its regulators prominently on a manufacturer's label even though its primary function is above all to provide after-sales service.
Today, this fascination with serial numbers persists among collectors. For example, a Mistral regulator bearing the address Cognacq-Jay will have a much higher sentimental and commercial value if its serial number has only two or three digits rather than four. Yet, all these models date from the same production year: 1955.
CG45s without manufacturer's label with PRO or standard bowl
At that time, diving cylinders were not equipped with bases, which prevented them from being stable when upright. This led to frequent drops, causing deformation of the regulator bowls, necessitating their replacement.
To meet this need, LA SPIROTECHNIQUE offered bowls as spare parts in its catalog. Around 1948, it is likely that it provided a manufacturer's label attached to the front bowl, stamping the regulator's serial number on it. However, this method quickly proved too cumbersome for after-sales service and was abandoned.
From 1950 onwards, only front bowls without a manufacturer's label were sold. This is why many CG45s have a humidity chamber without a label or traces of the four small rivet holes that secured one.
Contrary to popular belief, these models are in no way military CG45s. Nor should they be confused with the early 1946 models, known as archaic models, whose serial numbers were engraved directly on the back body.
It is also possible that at the end of CG45 production, LA SPIROTECHNIQUE assembled a final series from remaining spare parts. These models would have been delivered without a manufacturer's label, as it was out of stock. This hypothesis is supported by the fact that the last CG45 manual, published in 1955, exclusively shows regulators without a label.
The absence of serial numbers on these CG45s, however, makes their precise dating impossible.
CG45 sans plaque constructeur à gamelle PRO.
Détail de l'embout PRO.
Détail de la gamelle arrière du CG45.
Détail de la gamelle avant du CG45 sans plaque.
Photo du fascicule CG45 de 1955
Photo du manuel technique du CG45 de 1951.
The archaic CG45s without a label and without a serial number stamped on the HP body
These are simply old regulators equipped with an SARL label!
As in the previously mentioned case, damage to the regulator likely required the replacement of the pan.
To my knowledge, only one example is on display at the Dumas Museum in Sanary, assembled in hookah configuration.
 Détendeur CG45 à gamelle archaïque sans plaque constructeur et sans numéro de série estampillé. Exposé dans la collection du musée Frédéric Dumas à Sanary sur mer. |
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The CG45 with large SARL label mounted in PRO bowl
This was simply a modification made by its owner at the time.
The CG45 regulator had the advantage of being convertible and modular, allowing the rear bowl and the archaic exhalation nozzle to be replaced with a standard PRO nozzle, without any adjustment issues.
This modification allowed the regulator to be adapted for use with the PHOQUE constant volume regulator.
Détendeur CG45 à grosse plaque SARL monté en configuration PRO. Il s'agit ici du numéro de série 1080.
Détail de la gamelle du CG45 à grosse plaque SARL numéro de série 1080, en configuration PRO.
Analysis of CG45 serial number 516
In conclusion, this is undoubtedly one of the best examples illustrating the difficulty of dating certain CG45 regulators.
At first glance, this is a small SARL label model with an archaic bowl, equipped with the rare and legendary FERNEZ-type mouthpiece from 1946. We could therefore deduce that it dates from 1949, since its label is attached vertically, in the same way as the large SARL labels, mounted with their length parallel to the base of the exhalation nozzle.
From 1949 onward, all small SARL or SA labels found appear horizontal when the regulator is mounted on the block, forming a 45° angle with respect to the base of the exhalation nozzle. Indeed, before this date, the pan pipes were positioned horizontally relative to the plane.
However, upon closer inspection, we notice that its serial number is 516, which does not correspond to the chronology established so far. Turning the regulator over, we discover that this number is stamped on the base of the HP body.
There is no doubt, then, that we are dealing with an old CG45 without a label, dating from 1946, which explains the presence of the FERNEZ mouthpiece.
What happened? It is likely that its owner wanted to add a manufacturer's label or that the front body was replaced following a fall from the diving unit.
In hindsight, this modification seems to date from the beginning of 1949. It is likely that at that time, LA SPIROTECHNIQUE offered spare parts for cans with a small SARL label positioned vertically and stamped the regulator's serial number on it.
Détendeur CG45 numéro de série 516. Un détendeur atypique dans sa configuration.
Détail de la petite plaque constructeur en SARL.Ce qui interpelle c'est le numéro 516 (année 1946) qui ne correspond pas à la chronologie du détendeur car les petites plaques SARL verticales datent de 1949.
Vue de la gamelle archaïque du détendeur avec mise en évidence de la buse courbée d'expiration.
Détail du corps HP du CG45 avec son numéro de série estampillé ce qui confirme qu'il s'agit d'un CG45 de 1946, d'où l'embout de type FERNEZ.