Originally Posted by MNruss

I bought a 66-1 snub marked “BDPS” (Baylor Department of Public Safety ?)
that had something similar. I reckoned them at about 3/8” so pretty close in size. I don’t know if I could lay my hands on them, but iirc, they looked like small pinch-type hose clamps, but sort of reverse-sprung, to cling to the chamber walls.

Regards

Russ