A complete and functional, but not like new, 12 gauge utility double is worth $150-$250, depending on exact condition and its appeal to the prospective buyer's eye.
50-100 USD
Check out gunshop.com,they got Lots of info on dbl barrel shotguns.
Hammerless
delolosi
50-100 USD or so
It is only worth what the person buys it for...
Try gunstocksinc.com
50-100 USD
404019
You can find information for the 16 gauge Worthington Challenger single barrel shotgun at most gun stores and pawn shops. Many of these stores offer free appraisals and have knowledgeable clerks.
I have a Spencer hammerles shotgun, and it has America 's new hammerless on the barrel