Hello ceos55: well that's an early gun, made before 1927, so it originally had a 2 9/16ths chamber. Since you say it shoots wonderfully, I suspect it's been opened up to 2 3/4 in. Trust me, you would have ejection problems if it had not been.
So the gun is considered not original with a longer chamber. Assuming it still has the original "Pearch Belly" butt stock, about $200-$300 in the condition you described. Again assuming it's a plain barrel, and not a Solid ribbed barrel.
Any given week between Gunbroker, AuctionArms, or Gunsamerica you will see an early 16 or 20 ga come up. Mosst people don't know about the short chamber. some were sent back to the factory to be opened up. But most were done by gunsmiths in the late 20s and 30s, after the 2 3/4in shell became standard.
Regards Dave