So I finally found a 1958 336 RC. Got it for a decent price I think, $360 delivered. Finish is thinning on the bottom and the lower edges of the receiver but that seems to be common on many of the used rifles I looked at. The front sight has some marks from replacement. Screw slots are all clean with no burrs or damage and the rifle generally seems to be in good shape. The stock is clean, no sign of being sanded, no extra holes and the fit to metal is excellent. One exception to the condition is the hammer tang. It looks as though the top grooves of the hammer tang or thumbpiece were ground away and the underside was slightly buggered up also. I speculate someone had a hammer extension on it at one time. My question (finally) is what changes happened to hammers for the various 336 models over time. Can I use a hammer from any 336 of the same or similar vintage? I have noticed that some hammers have a groove on both sides, presumably to allow installation of a hammer extension. I don't recall if my hammer has such a groove or not. I would prefer to replace it with a used hammer that matches the finish wear to some degree. Thanks for any info and will try to post pics this weekend.