I too purchased a Calypso in the 1971-2 period. The second stage has "J" printed on the purge button so it was a standard model, not a retrofit. The first stage has a main low pressure coming out the end, and 2 more on a turret. There is only 1 high pressure port coming out at an angle from the bottom. Patent Number: 3.426.790---- The serial is 411244.
The sucker still works. At one point in its career I raised the IP some and connected a Cyclon 2nd stage to it. The part I liked about the "J valve" feature was that when it kicked in it made breathing difficult, not impossible, so you could still breathe while hunting around to turn the J (I never used a pull rod). I too remember that the Scubapro w/ BRA had just come out. I do not remember the Calypso being a hard breather. In fact, it was the early scubapro's that I thought didn't breathe very well, knob or no knob. It could be a little wet somethimes. Wow, this is a flash from the past!
