Is your friend the original owner of this gun (did he buy it new)? I was thinking that the best way to determine a fair price is to see what they're going for on auction sites (
www.gunbroker.com and the like). You have, basically, guns from 2 different backgrouds to consider. First is guns that have been wholly privately owned. Second are the LE turn-ins. LE guns are going to be worth less than privately owned. They're typically rougher and have been handled a great deal (so the finish suffers). On stainless guns this is exhibited by burnishes on the stainless steel. Most LE revolvers were carried alot but shot relatively little (some no more than 50 rounds per year of service). They can still be tight and in mechanically excellent condition. Private guns hold a premium. They're usually better finishwise and, many times, have been babied quite a bit.
I would say a pristine wholly privately owned example would be in the neighborhood of $350. This is quite a bit more than your friend could hope to recover from a gunshop and about fair for a private sale. Not pristine? Maybe $300.
LE turn-ins would top end at $300. Lots of finish wear but good mechanical condition would bottom out at $250.
Ask him what he's looking for pricewise, then see if you can meet him in the middle somewhere.
I generally seek to avoid firearms deals with friends. I don't want a situation where somebody comes away feeling cheated or shortchanged. I've given a friend real sweetheart deals to friends on guns before. Quite a bit less than I could have gotten on a private sale, but I got what I thought the gun was worth.
