Winchester Model 12's (1912) have a distinctive bolt design. That's how I identify them. It looks like a 12ga but there seem to be a lot of 20's and 16's out there. I've always wanted one and if I got one from a family member it would be a treasure to me. When I hear the phrase "they don't make them like they used to" the model 12 comes to mind. They stopped making them over 50 years ago I've seen some that look worn but work great. It's a definite American classic.
I have also seen some come out of the old Mossberg Custom shop that look very similar with the jeweled bolt. I used to have a 12ga. that did. Beautiful shotgun. I do appreciate then, but I am really not a shotgun guy.