ID a .303 Martini Sporting Rifle (and find a firing pin)

Hope someone can help me identify the Martini .303 Sporting Rifle I just acquired. It was sold as an 1876 conversion, but I don't think it is. It's a fine old gun -- sporting stock with cheek rest, Williams sights, chambered for .303. Typical British proofs (notably BY Crown) and marked "303 nitro proved." No military markings, inside or out. Any ideas on who made it? BSA? Parker Hale?

Unfortunately it has a missing firing pin. The pin body is still there but the pin is missing, and there is a hole where it used to be. Anyone know where I can get a replacement? I am told that the .303 breech blocks and firing pins are different than the .577-450, so I'd appreciate some info on it. BTW the breech block is stamped 10x.

Long Ranger,

The "standard fix" for a broken firing pin on a Martini Enfield rifle is to have a short piece of drill rod of the proper diameter soldered into the firing pin. If you an't do this yourself or know a reasonably skilled gunsmith (not a parts-changer) I suggest you contact Brian Dick in Edgefield. About Us
Brian is very knowledgeable about British firearms and easy to work with.

Is there by any chance an encircled E or an encircled V stamped on the barrel?

Try Peter Dyson in UK for a new striker..

MARTINI HENRY Parts

These are .577/.450 but he may have some .303 ones in a box somewhere...!