The 'factory engraved' Winchester Model 12 is probably one of most 'humped' (to use a gun show/dealers term for faked) guns around. Those and the Winchester Model 42, Model 70 and the Winchester pump and semiauto 22s.
There are no Winchester Factory records on the m12, nor the m42 engraved guns.
There are the Kusmit personal records and other 'experts' opinions by looking at particular specimens that they are or are not factory engraved.
The experts opinions on originality are worth just that.
The fact that the gun had to be re-blued after any aftermarket engraving was done is the biggest giveaway to look for.
Factory work was done on the factory polished and not yet blued finish. Then the gun was blued after the engraving.
The Winchester Proof marks should be punched through the bluing,,not be under the bluing. Another easy to spot item. But the fakers have the proof mark stamps. Easily made or even for sale now a days to make your own Winchester look right.
Any Model 12 with a factory engraving pattern that extends onto the bbl would NOT have the WinProof mark up close to the breach as normally seen. That area was reserved for the engraving scroll pattern.
Even the Winchester bbl marking/gauge and shell length mark was usually moved forward to allow for the engraving.
The bbl proof mark when applied to the completely engraved and finish blued gun was struck ahead of the engraving towards the muzzle.
The factory engraving patterns are published in several books. They are not particularly difficult patterns to cut and variations are and were expected in them. Customers could select wildlife image differences in the patterns as well.
Riffles book is a good reference but many of the M12's in that book are upgrades done aftermarket.
A certain engraver did most of them and even did a few glaring mistakes but the guns were included anyway.
The flow of aftermarket fakes overcomes the real stuff out there and after a while know one seems to know whats real and what isn't.
Add to that the fake paperwork, boxes, hang tags and even Custom Shop letterhead and envelop correspondence.
The Custom Shop paper itself is real and is typed on the same typewriters used in the actual Custom shop.
It's just that it was never done IN the C/Shop. All that stuff went missing from the NewHaven location after it closed up.
Type up what ever you want it to say and date it as you want.
The same situation exists with the upgraded, excellent condition, NIB, w/paperwork and correspondence Winchester Model 61's, 62's and 63's around.
No factory records, Winchester made probably a handful at best Deluxe models of each. But now there's 100s of each around.
As far as a engravers signiture marked piece. The same old standby adage applies... 'Who's name do you want on it and where?'
Buyer beware. This is the reason many seasoned Winchester collectors have stopped buying M12's, 42, the 22's and the M70.
Late M12's were mostly sent out (farmed out) for engraving.
Engravers like Bill Mains when still in Buffalo NY did large numbers of those. I don't know if the guns were done by Bill under contract w/ G&R Tackle in W.Seneca NY where he did most of his work thru. G&R had Bill quite tightly tied up in a contract to do engraving but I don't recall if it was entirely exclusive or not.
Mains was also cutting Ithaca SBT guns at the time.
Used to drive him crazy sometimes doing that repetitive factory work. To get a break he'd get on his tractor and plow up some of his small garden plot just to get away from it.