The Conshelf is a workhorse regulator who's design goes back 70 plus years. I cannot tell you the abuse I have put them through commercial diving. I have hooked the first stage to a K bottle lying in the floor of a boat, ran 150 feet of hose to a band mask, and worked all day in 30feet of water cutting off piles. I have hooked them to a stage bottle and ran impact tools and drills off of them at 100 feet. I have personally used Conshelf's in 270' of water at Dipolder on air. The Conshelf first stage was a standard bail out regs for sat divers.
The only part you need to buy is the high pressure seat, and occasionally a filter. You can buy a plug punch at harbor freight, a piece of red gasket material the correct thickness, and punch out 50 2nd stage seats for a few bucks. The rest is o rings.
If you find someone that knows how to tune them, they are a fine regulator. If you don't want it, please send it to me, I will fix it and add it to my collection.