Re: bay state 410 shotgun
Bay State was a Trade name used on H&R shotguns prior to WW II. I know of no parts source for these early shotguns other than a parted out like item. I did a little checking on several known parts sources and no joy. If you have the old firing pin then it would be a simple matter to have one made. If you own a drill press you could do it your self out of a drill bit. If you no longer have the firing pin , well , that's a problem. You have to find a old parted out Bay State or H&R of the same vintage to salvage a usable part or pattern.