so last info just came in:

the rifle in question is a Alexander Henry serial no: 5840

it was delivered as no. 1 of a pair of 12 bore rifles on the 10 march 1885

the bore of the rifle is somewhere between 0.751" and 0.763" the grove i do not know yet.

the chamber is 12 bore chamber allthough a bit oversize. so 12 gauge brass is the order of the day.

the load as a 12 bore would be around 8 drams and a conical around 750 grains according to the book holders.(big bang)

this is it so far, i wait for the papers to arrive, and then im off to merry old england to pick them up.

best regards

peter