Use gunbroker. If you search for completed auctions then you can find examples of guns and what they sold for. I wouldn't trust anyone to give you an appraisal your best bet it to use online sources. The last place you want to go is some random gun store as they only contain people who know nothing about guns, but think they know everything about every gun built from the beginning of time. not always there are some good guys out there but there is no way to know unless you educate yourself first.