Gauge question

[D. Shane Burton]

I just bought two old Parkers, one from 1901, which I'm pretty sure is a 16 gauge, and the other from 1899 that I think is a 12 gauge.

I placed a modern 20 gauge in the one I think is a 16 and it was too small, while a regular 12 gauge was too big, so 16 gauge it is, I'm assuming.

Now, on the one I think is a 12, the modern 12 gauge shell seemed loose in the chamber, yet when I tried to put a modern 10 gauge shell in the chamber it was too thick to fit. My question is, were the old 12 gauge shells a bit thicker around the turn of century, or were the 10 gauge possibly tighter? Do I have a 10 or 12? Going by the frame size, which is a 2, it could be either. If my dad can find his inside micrometers, I will have him take readings on everything, but what do you guys think the deal is with the gauge? By the way, the barrels are 24 & 5/8inches long from their tip to where they meet the receiver area with the firing pins.

Tonight, when I get home, I plan on posting threads about each of my Parkers with pics, but I just wanted some feedback first.

Thanks for any help or advice. I'm new to this.
Shane