The action part of the gun also had proof markings on it. It has the proof that is under the Birmingham House , the one with the crown, crossed arrows and the V under it.
I was unaware of there being proofs on this part of the gun. Here is a pic of it...
If anyone has more info to add on this it would be accepted with thanks.
Incidently I measured the inner diameter of the tubes and they are almost identical. Would the 13 and the 14 be showing the gauge? What would the reason for these numbers be? As well as all the other numbers stamped on the underside of the barrels?