The coupler and screw, plus the lever screw, should be available from Numrich Arms (e-Gunparts.com) I have a copy of "Plans and Specifications of the L.C.Smith Shotgun" by Brophy...If you can give me more info, I may be able to find a drawing of the firing pin so that it can be duplicated..Need serial number (or year of manufacture), etc. Am not an "expert", but am willing to help you all that I can.I have been "blessed" with info from this site!