Oh yes there's a price for that gun, unfortunately the auction sites are all over the place. guys are running up their own bids pretty regularly so a current value would be difficult with this one.

Here's what the Bluebook says , it does actually seem to be about right.
Grading 100% 98% 95% 90% 80% 70% 60%
12 ga. $525 $395 $325 $295 $225 $175 $150

 

sounds like you have one of the early PROOF STEEL guns. Winchester swiched from nickle steel to proof steel in 30/31 and shortly therafter eliminated the pattent dates on the right side of the barrel. Id bet if you barrel is original to the gun that the serial number is in the 625000-700000 range.