Patrick;
There is nothing on your gun that tells you it had "Exactly" .719" bores when proofed. The 13/1 tells you it would accept a .719" diameter gauge 9" down the bore, but would not accept a .729" (12ga) one. It could have thus been anywhere from .719" to .728". 1 1/8oz was the standard proof for the nominally chambered 2˝" gun. The chamber actually likely measured from 2 9/16" to 2 5/8" (65-66.7mm) but the Brits called them 2˝". This 1 1/8oz was the service charge, not the proof charge. A gun of this era carrying 2 3/4" (70mm) chambers was required to pass the heavier proof for 1Ľoz of shot. The former was essentially a 3-ton proof & the later a 3Ľ-ton proof. These amount to approximately 8960psi & 9800psi as service loads.
