What a fantastic duo
AFAIK the Scubapro 500 came out in the late 70s. Here is a picture I found on the net which shows the 500 (automatic version) on top of a Feb. '78 Skindiver mag SP ad:
(pic found here: http://www.network54.com/Forum/78440...an....%26gt%3B
The Nivada Depthmaster is simply amazing