Just looked over your listing and fotos ed. Cool gun!
Id never restore it but given its a no name Belgian id give it a good cleaning and some sympathetic work to the wood finish- if it were my gun that is.
Nominal bore size for 6 gauge is .919"
Did the bores measure exactly .900" ath the muzzle? If so id bet it is a 7 bore


I may have been born at night...but i was not born last night!!!