The first Jet Air circa 1956 was made of a brown plastic compound with raised lettering. It was a cheap alternative to the more expensive brass case regulators of the day. I fact the plastic case with 6 screws was probably a superior design and definitely sealed the main diaphragm. This regulator is very unique looking and is beautiful in is ugliness. These cases prove to be very durable and resistant to corrosion. The internals were basically a Stream Air.