Search Gunbroker and other online auctions. Ignore pistols with no bids. Condition is everything on these along with originality. Good luck. Also be careful of gun show valuations from interested dealers. Everybody who sells these is not an expert.
I bought a friend of mines Remington Rand and I think we looked in a Blue book of gun values. I can't remember exactly what the prices shown for fair, average and excellent were. We decided that it was in average to good condition, it shoots very well and settled on a price of $500 bucks. Maybe it was a little low but we were both happy. His dad had it issued to him in the Navy during WWII. I'm glad to have it!