The Royal Aqua Master, the king of regulators: the successor of the well proven well established Aqua Master, but with the major improvement of a balanced first stage.
The balanced first stage is not affected by tank air pressure allowing a very stable intermediate pressure. Since the balanced first stage is not affected by tank pressure, it also allows the use of a larger volcano orifice for higher potential flow rate.
The direct predecessor of the Royal Aqua Master was first introduced in 1964 to 1965 as the Royal Master. The Royal Master had a balancing chamber with only one O-ring (no back up ring) and a small spring pushing a washer to hold the O-ring in place.
In 1966 the Royal Aqua Master was introduced. The only mechanical difference from the Royal Master being in the balancing chamber; the small spring was dropped and a lip was added to the balancing chamber to hold the O-ring. The back up ring was added a year or two later to avoid O-ring extrusion due to high tank pressure.
The back-up ring in the Royal Aqua Master was added years before the common use of 3000psi (and higher) tank pressures, but it has allowed the design to be used at most any modern tank pressure without concern of O-ring extrusion.
The design of the RAM first stage has been so successful that has continued to be the primary first stage design for most US Divers/ Aqua Lung regulators; it is used on all the Conshelf, Titan, Mikron, etc. Not only has the mechanical design not changed, but the parts are actually the same.
For more information about the Royal Aqua Master and the differences between the RAM and the Aqua Master look at the links below:
http://www.vintagedoublehose.com/forum3 ... =12&t=1948
http://www.vintagedoublehose.com/forum3 ... =12&t=2182
From 1966 to 1969 the RAM fashioned the familiar rectangular ID plate with a large gold crown that dominated most of the tag, with a perimeter of blue
In 1970 to 1973 the label was changed to the large silver round label.
In 1973 it was the last year of production for the Royal Aqua Master. Units were still available for a couple of years until inventories were depleted.