Pics would be helpful. Are you talking private sale or to an ffl or evaluation for insurance? For simplicity and a quick answer I'll usually just check gunbroker. Guns are worth what people will pay for them just like any other "collectable".
Cgig- I moved your post over to auto pistols. You posted in the section for suggestions for the website.
BAD CGIGGITY ! BAD ! No cookie for you!
Just kidding- no harm, no foul.
WHile I have several references at the house- they tell me what that gun sold for a few years ago. Want to to find out what it has been selling for recently?
Go to gunbroker.com and register with them. Once registered, search, advanced, COMPLETED auctions, enter info on your gun- and it will pull up the closed auctions for that pistol. Be sure to look for ones that SOLD, not just ones that were for sale.