Hey Bob: that might be part of the serial number. Usually the Toks, at least the Chinese Toks had the serial number stamped on both frame and slide. I have seen a couple of TT-33s that, iirc were stamped only on the frame - those were Ruskie pistols though. On occasion though you may find one with some lettering engraved on the frame which, depending on the interpretation may mean either 'save the last round for your dog, or for your mother-in-law' but those are hard to find (I think the dogs ran off with them for self defense....). I once had a 7.65 mm Luger with a 6" bbl that was supposed to have been purchased for the Royal Siamese Guard and that had a Thai inscription on the grip that was interpreted as 'save the last bullet for yourself' but that had not been confirmed so I dunno.