I mic'ed the chambers, and they are dead-on 12 gauge, so we might have a mystery here. Plus, I've been shooting this gun for over 30 years with 12 g ammo, and have reloaded the empties with no signs of oversized chambers.
The bores are certainly oversized for a 12, and the chokes are a very long taper in both barrels.
I suspect that this was a pigeon gun, so there's no telling what interior mods might have been done over the years.
BTW, this gun patterns nicely, and kills pigeons in the ring with authority!

Some more info: The barrels weigh 4.14 lbs, the FE 0.54 lbs, and the receiver/butt stock 3.86 lbs, for a total weight of 8.54 lbs.
Based on being a 3 frame, and weighing 8 1/2 + lbs, I'm guessing this gun was built for some heavy duty work.

This gun was almost certainly made with 11 gauge barrels. The Parker Story discusses this in some detail. Part of the reason was the original chambering with thin wall brass shell ID. The 12 gauge standard was an 11 gauge barrel and the 10 gauge standard was a 9 gauge barrel. It even gives a date in the 1890's when there are notes in the factory books stating that future barrels would be to gauge unless stamped "O" to signify the older size. It's pretty explicit in the book, but I have found no way to verify it.

Serial #3371 has bores that are .756" and 12 gauge standard shells fit perfectly in the chambers. The Serialization book lists it as a 12 gauge. 12B shells rattle in the chambers.

Wayne, those dimensions are pretty much the same as my gun.

As far as I know, the entry of 12 gauge means that it is chambered for a normal 12 gauge shell. It has no meaning as to the actual bore diameter of the barrel. I don't own a lot of Parkers, but most of the ones I do are from this time period. None of them have regular 12 gauge or 10 gauge actual bores. If the records from that period were listed as actual bore diameters, most of the early guns would be 11 or 9 gauge.

Looks like this gun is changing hands. More later.

I believe, like Art S., that it is chambered for the 12A shell (it even shows 12A shells as being part of the order) but the barrels bored to 11 gauge.
Todd says it is a 3-frame even though at 8 - 8 1/4 lbs it would seem to be on the 2-frame.





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Dean, what I thought to be a "3" on the lug appears to be an "S", so I'm not sure.
I did a measurement between the firing pins, and the spacing appears to be 1.17" center to center.
The gun remains a bit of a mystery, but I believe it to be an important piece of the puzzle of the Parker company's high grade gun evolution from back in the 1870s

I agree, it most definitely is that Todd.
1.17” = 1 3/16” and that is the pin spacing for a 3-frame.





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