That is one very nice rifle and it is most certainly factory engraving, probably an "F" grade which is top of the line. I am not much of an authority on Model 12's but can tell you that your gun falls into late 1912 production...........like October. Your rifle looks to be in extremely good condition, has significant value, and is very collectible.
I've just passed on what I know, be patient, and you will get better feedback than mine.
Lovely gun!
Thank you so much for your reply.
The rife shoots well and is very clean.
Barrel and riffling are also very clean.
Shot it a lot as a kid and just forgot about it for 40 or so years until our move.
Since then it have been checked out mothballs knocked off and fired at the gunsmiths shop last year.
Borescope pics to come.
I would not shoot it other than to make sure it works, a rifle of that quality needs to be admired, and "any" bit of wear might significantly lessen the value. It is in my opinion super-high collector grade and quite valuable, lovely gun.