colt new service 44-40?

Friend of mine has a new service in 44-40. I didn't even know they came like that. I have my grandfathers that was .455 but was rechambered to .45colt by colt.The bad news is it has been replated in nickel so it isn't original and has some smooth black stocks which I sure aren't original.So he asked if I wanted to buy it. It is a colt I don't have so I am definitely interested but no idea what I should offer him that is fair and not a serious low ball.