Brian ,I was thinking with the Barrel weight ,it may in fact be a 16 Ga. # 1 Frame Gun or possibly a # 1 Frame 12 ?? As for the owner knowing ,Maybe/ Probably ,but I just recently purchased a Miller @ Val Greiss Drilling and thought I was buying a 28 Ga. Ends up it is a 24 Ga.!
And like a Dummy ,I even admit to it on the internet !