Here is the first major series of the ROYAL MISTRAL released in 1963, it has no HP output. It has the first generation AQUASTOP mouthpiece and the plate has a dark blue and golden yellow color, it has the serial number 8681.
Here is a version of the ROYAL MISTRAL with a PRO mouthpiece. It is DIN mounted and has a male pressure gauge output with imperial thread. This model was intended for the German market and has the serial number 34182, probably dating to the year 1972 and therefore it is one of the very first ROYAL MISTRAL with an HP output.
I present here the model of ROYAL MISTRAL released in 1972 with an HP output in 6/100. This one is new and comes with its 1978 purchase invoice, serial number 52285.
Here is a first generation of the ROYAL MISTRAL without HP output. The blue gray and pale yellow plate is numbered 40853 which dates it between 1967 and 1969. It is mounted in DIN and it is my second ROYAL MISTRAL bought from an old German diver in Ibiza in 1997.
Above a very nice copy of ROYAL MISTRAL intended for the English market with an "i" seat 17.8mm in diameter. It is equipped with a male HP outlet with imperial thread. It has the serial number 50744 and probably dates from 1977.
Here is the second generation of the ROYAL MISTRAL released in 1980 with a 3/8 HP output. The black plate numbered 58232 no longer bears the name COUSTEAU-GAGNAN. This regulator is equipped with the NAUTILUS tip of the ERUS submarine communication system and probably dates from around 1984.
Here is a second generation of the ROYAL MISTRAL released in 1980 with a new 3/8 HP output with its box and whose black plate is numbered 56784. It is a relatively rare item to find.