Here's the deal, and I'll by-pass the story of how all this came about. Currently in my possession I have an OOE Grade, "R" frame, #212012 from which is missing the lock-plates, stock, trigger guard, and maybe another part or three. The original ejector barrels to gun #212002 are also in my possession and have an ugly 3" hole in the side of the left tube about mid way of its 28" length. There is no fore iron; and the gun would be a total wreck EXCEPT for the fact that, with the gun, is a factory replacement barrel set, numbered to the gun and in near new condition. Oddity No. 1 is that I have never seen a wrecked set of Smith barrels that have managed to remain with the gun once those wrecked barrels were replaced?
OK, so this replacement set of barrels is numbered to the original "R" frame and are the same length as the original barrel set; BUT this replacement set is fitted with manual extractors and not auto ejectors; and this new barrel set has the raised single sighting plane rib introduced in 1938, and which eventually became a standard feature. Unfortunately there is no fore iron with this barrel set either; but the high rib feature clearly indicates these factory fitted and serialized barrels were done very late. which brings me to oddity No. 2. Besides a serial number stamp, this later set of barrels has the "NP" nitro proof mark stamp, but is not stamped as to grade (no barrel flat grade stamp; no roll-stamp atop the barrels). But it does have one stamp I have never observed on another set of Smith barrels; on the left side of the barrel lug directly above the cut for the extractor retaining screw is a small oval inside of which appears to be stamped the letters "JM", a stamp seen on the barrels of Marlin rifles prior to the Remington acquisition of that company. If those letters are indeed "JM" (and I'd post a pic if I had the intelligence to do so), then I would interpret them to denote "John Marlin"; and would then assume that this barrel replacement work was performed something during the 1945-1950 Marlin ownership era. So my question to the real experts; anyone seen a similar barrel stamp? If so, what does it mean?