A friend of mine just picked up an "old" rifle as part payment for a roofing job. 4 digit Marlin M93, with an R suffix, and a star cartouche stamped "JM" in a circle, (inspector?). How do I found out how old this is? Marlin serial numbers seem to be all over the place. And, assuming that it is generally safe for Sammi smokeless loads, anything in particular I should look at in detail before cleaning it up and firing it?