a good gun smith can repair your old firing pin or make one. gunparts Inc of NY could have one, but I doubt it.
find a smith in your area and let him make one.
It would just be called a Forehand Arms Single Shot.
1890-1930 or so
Hopkins and Allen purchased Forehand Arms in 1902, so sometime between then and 1915 when the company closed.
Hopkins and Allen took over the Forehand name in 1903 and continued until 1915.
$125 dollars
http://www.e-gunparts.com/productschem.asp?chrMasterModel=0840z500
Possibly a broken firing pin.
How to replace a firing pin from a Charles Daly 20-gauge semi automatic
firing order of 1971 VW
There was a Browning 12 gauge with the patent 2203378-223386, that was sold for $999.00 at an online auction.
It is worth $50, give or take fifty dollars.
$500