I don't know about any 'book' value, but for myself, I think $250 would be a fair value. I don't believe I would want to pay over $300. That was a neat gun (a little weird in the grip shape, but I think you could have a standard saa style grip installed) but they have no collector value, only curiosity and as a shooter. It's good he has brass as that is often hard to find. If you come to a price that suits both of you, be sure to post us some pictures. 44 Man