Alexeander Henry Falling block info wanted from other owners

Just wondered if any forum members who own an Alexander Henry Side Hammer falling block rifle could make contact and answer a small technical question about the firing pins on these.

My one is new to me, but 149 years old and the internet clearly doesn't know everything.
I still need to grind a special socket to reach into the breech block rebate and extract the firing pin, which is a bit like a precussion nipple tucked inside the block

cheers