When I need to know the approx. value of a firearm I just log on to GunsAmerica.com and see what that certain model is going for.(other auction or on-line sites will work) You can look at multiple listings on this site and get a good idea. I used to go by the Blue Book of Gun Values but the prices are too low.(especially if your a seller). Just one example: I sold a Rem Model 11 16ga. for $450 in a short period of time, the Blue Book listed it in good condition for around $250-$275. If you are a buyer I can see how you could use the Blue Book to your advantage, though. Not exactly an answer to your question, but I hope it can help you in some way. Granted, in different areas different guns command a better price.