On Monday, December 10, 2018 at 2:52:00 PM UTC-8, bob prohaska wrote:

I suspect a lot of these valves were used in the '50s and '60s and
quite a few of them are still in service. If I knew what they're called
it's likely I could find a wrench, or at least what the wrench looks
like.

I don't have any machine tools except a lathe, so cutting a pair of
accurate wrench flats will be a "file and fit" proposition.

Yeah, that's do-able; just turn a thick disk, mark center and scribe lines
at 3/8 inch either side; hacksaw through half or less of the thickness
near those lines, and grind out the middle.

Then fine-tune with a file until it fits. Extra credit, weld a pipe onto the
disk and make a T-element on the other end of the pipe for a handle.

Actually, welding a couple of bars onto the endface of a pipe wouldn't be too bad:
clamp a right-thickness chunk between 'em to keep parallel.