[LMH]

They were made of cast iron early on and cast aluminum later. I looked a long time before I found mine though I do think it's a reproduction. The machine work on the switch mounting surface is machined differently than the one in Dan's photo. Mine is cut by a pass across the gasket surface and Dan's looks to be cut on center.
I don't know if the coupes used them or not.

The broken bolt that was in mine fit in a U.S. 10-24 die quite well. I ended up running a 10-24 tap in the holes and it turned out that I really didn't cut much of anything thread wise. Another reason I think mine is a repo.

The tube could be fabricated out of tubing and that was my plan but I was lucky enough to find one used, so didn't take that route.
Larry