Ref. the 16 bore. If it's marked 1oz. it should have 2 1/2" chambers. 23/4" chambered 16 bores were marked 1 1/8th. ounce.

You'll not find a bad Harper gun. He mainly made for the Trade; a sort of unsung hero of the gun trade, and seldom sold guns under his own name. Lagopus.....