I have a buddy who wants to sell me a 3rd edition Colt Det. Spl. nickle finish. It has sat in a leather holster for over 20 yrs. All the area of the pistol that was actually inside the holster, has taken on a satin looking finish. From about the rear of cylinder to the back, its super shiny. I actually like the satin look, is there a way to get the rest of the shiny part to match? Not sure what can be done to nickel finishes. I really dont like shiny finishes.

No real way to make the whole gun satin, but you could use an abrasive paste like Semichrome to bring the whole gun back to original luster.