Found this peep sight in a box that my neighbor gave to me with a bunch of reloading stuff. I bought a Marlin 336 from him a few years back and it had a Williams peep sight on it and I thought that this sight was just another attachment for the one that was on the rifle. Took a closer look at it yesterday and found out that it was a completely different sight. The problem is I don't know what type of mount it attaches to. It won't clamp on to anything I have. It looks like it is about 16mm across the bottom of the dovetail. I've tried it on a Marlin 39A, 10-22, and an 1894 with a scope mount rail. Nothing fits. Any ideas? The only marking I can see is "made in Finland" and the numbers 100 and 200 on opposite sides of the appature.