Alright, I had a look at my Model 12 and checked for the items that you mentioned, Rod.
The bolt is quite sturdy, it does not move up or wiggle at all when I press from the follower underside. I also cannot see or feel any burrs or bends in the lock up notch.
I have not taken this Model 12 down myself as it was quite clean when I got it. The left side of the receiver where the take down looks to take place has some wear marks so I imagine it has been done before me. It does wiggle a little bit when I grab hold of the portion forward of the receiver and twist left and right, however it still feels tight. I have attached a picture of the area as well.
I also had a look on the barrel and I was incorrect about the patent information being present. The "Made in New Haven, Conn.", Winchester trade mark, and shotgun information are still present and clear to read.
You are right, these shotguns are well made. I would rather not sell it but if times this September demand it to fund college, I may have to. Since shotguns are not my area of expertise, I greatly appreciate the comments on it's value.