The barrel, frame and cylinder are all stamped with the number Q2179. The problem with the revolver did not manifest itself until I went out to shoot it. The heads of the cartridges were so tight against the recoil shield the cylinder would not advance when you tried to pull the trigger. I started troubleshooting by measuring the space between the shield and the back of the cylinder with the cylinder held forward and the thickness of the rim of the cartridge. With the brass measuring .056 and the space measuring .049 the reason the drag was plain, the question was why, what should be and how is it supposed to get there started the search.

When the shim was discovered, the questions multiplied!! Is this supposed to be here? Is this how the fore and aft float is controlled? This one seems too thick, do they come in sizes? That quest lead here.

With the shim out, the cylinder will just rub enough to remove a chalk mark on the edge of 2 chambers, so that clearance is minimal. The clearance at the back of the cylinder is generous, it will pass a .070 gauge. I suppose if the firing pin is long enough it should go bang. That was suggested upthread, and shall be the next step.