Thanks for the detective work everyone. I'll go with John Martin from Cork some in the 1760's or 70's.
I took it out and looked it over more closely and took some pics with the Canon whenever I saw anything of interest. So I'll post those just for fun. Ahead of his name stamp is what looks like a teardrop-shaped fish and possibly a stylized duck ahead of that:
The only other stamp is an illegible tiny square stamp (not even 1/4"):
There might be some numbers engraved on the tang (back to back 6's and 9's) but the more it look at it the more I believe it's a face.
An owner carved their initials near the trigger at some point.
Someone mentioned yesterday that the stock may have been shortened. If so, they did a good job of it. If not shortened then I wonder why the dovetail slot? Could that have been for a sling?
And lastly, engraving on the butt plate.