My luck is consistent!
A while back I bought a 1959 OM with two cylinders at a gun show. And was quickly informed by this great group that was not possible! And, they were right; the barrel failed the 7/32 bit test. I had a .22LR only that was sold with an extra cylinder that did not belong with it! So I have an extra Magnum cylinder.
Yesterday I visited the local gun shop where I have bought several guns, and they know me. They had an OM made in 1965, serial # 414xxx. The Magnum series numbers, but stamped .22 Cal.
Had the extra cylinder, so things looked good!
Traded my 1981 New Model 6.5" barrel in on it. Didn't get as much out of my NM as I wanted, but did get more than I paid when I bought it from them a few years ago. Since I wanted a shorter barrel, and discovered I like the OMs better, took the hit.
Got home and tried the Magnum cylinder in the gun (Yes, I know, should have tried it there! But I trusted them to check their used guns out!). Didn't fit! Tried it in the 1959. Didn't fit.
LR cylinders fit both guns. So, what's up?
Got the vernier caliper out and checked the length of the LR cylinder that fit. Magnum was longer, and appeared to be "virgin" on the nose end; never filed to fit. Took it out to the shop, got a nice sharp file, and started to work on it. Got it fitted and squared, and it works great now.