I think that this could possibly to be an Irish made pistol,or made in Birmingham for the Irish market.It has a lot of typical 'irish' features, not least the large bore. Known as a
Manstopper. You know what they say '
A little powder,much lead,shoots far,kills dead.
I'll surmise you're thinking the name on the lock plate is 'NOCK' but's that's no guarantee it was made by Henry Nock. His name was frequently plagiarised to add a bit of polish to generic pistols like this one.
Maybe you have other ideas?
hard to read from the photos.
Niall