Yes that was a factory special order option and quite valuable. The hammer itself would bring $200-400 depending on the day and how much someone needs it. Humpbacks were first introduced as an option on N frame registered magnums. They were then made available on N frame .38-44 Outdoorsman, on K38 (and probably a couple K32s) target sighted guns and K22 Outdoorsman. I even have an non-target .38 M&P that has one I believe was a police dept special order. I find that odd though because you can't sight the gun in double action because the hammer is in the sight picture.