They are bushed, so were, as Captain said, made for breathing air or life raft use. They were made by "ALFCO", whoever that was.
I do, however, have a pair of diving specific Rene 38s by U.S. Divers made in 1954 with 1/2" tapered threads.
ZKY, this pair of USD 38s (you saw them at Stillwater) require about five pounds more weight than a single steel 72 in sea water (and also weigh 5 pounds more total dry weight when full than a steel 72, making for carrying 10 lbs more total when walking to and from the dive site).
