One of them - picked up at Nearfest as I remember - had a manual with it, and someone had marked "rec. 13 May 70" on it. Sounds about right, considering the construction techniques. I would imagine that they were probably quite expensive in their day. I've got three, actually, all different models but using similar construction, from the same manufacturer. See pictures attached. The one on the right has three outputs, with the top two ganged together and referenced to a common post, so you can get both positive and negative rails for op-amp work, and by using the "tracking" switch, you can adjust each rail separately or lock them together, and they really do track - each rail increasing or decreasing by the exact same amount - with impressive accuracy. The one on the left has digital meters, and again, the accuracy is impressive. I wish I knew more about the company; if they ever made a high voltage DC supply, for hollow-state work, I would love to find one!
Edit: just found this on the web
https://techobsessed.net/power-designs-power-supplies/Appx what year was that built? Beauty.
