Most English Blunderbusses will have the makers name on the lock and the location on the barrel.

1) English, Lock J Jackson, Barrel Cranbrook. 4 bore, or 1 inch.

2) Irish, Lock Parkinson, Barrel Dublin. 11 bore or .750

3) Irish, Lock Elton, Barrel Monaghan. 11 bore, or ,750

4) French, all marking were worn off or "cleaned off during restoration but style
definitely tells me this is a French gun. 14 bore. or .690 (Standard French military bore size)