Just some FYI for you MK 7 "Honker" fans.
The main thing to look for is the yoke and key thickness. In 1971, the 1st generation had a standard yoke that was capable of tank pressures of around 2600 psi, though many dove it with pressures of 2800 to 3000. Scubapro realizing that the industry tank pressures were on the rise to 3000 in and around 1977-78 started to increase the yoke thickness as seen on the 1978 model 2nd generation. This reg is more than capable of withstanding 3000 psi pressures, though it is not marked as such. Two years later, the 3rd and most beefy final variant in 1980 would be stamped with the 3000 psi pressure rating on its yoke. What started out as a beefy reg in the first place ended up SUPER BEEFY by 1980.