I, too, have always liked the squareback TG (I have a 2014 [CM] Pietta 1851 Navy .36 that originally came with the round TG but "upgraded" it to a Pietta squareback TG from Taylors'). Before you stated the date of manufacture, I was straining my old eyes for the date code and the proof marks. Could not see them even with those nice pics. Is it marked S. Marco (or similar) anywhere? Just curious as I have an ASM 1848 Pocket 6" .31 squareback w/load lever (marked REPLICA ARMS CO EL PASO TEXAS / MADE IN ITALY) that has the 2 proof marks (frame, barrel, & cylinder) and the date code XIX (1963: first year of manufacture) but not marked as an Armi San Marco anywhere (I have completely disassembled the pistol). I have it on good authority (Dr. Jim L. Davis:
http://rprca.tripod.com/ ) that it is an ASM.
I especially like your pistol because all of the screw slots are in
very good shape. You must have a very nice set of gunsmith (hollow-ground bit) screwdrivers and I can well appreciate that!
It is always appreciated when folks post pics of older replica C&B revolvers of different manufacturers/dates, along with posts like yours and others explaining what other manufacturer's parts fit other pistols and the degree of fitting necessary, even just for comparison. That's why I like the BP forums on every site I frequent.
Very nice, Canaris!
Jim