London marks.
Birmingham marks.
Mode of affixing Proof Marks.
On arms of the first and third classes the definitive proof mark and view mark shall be impressed at the breech end of the barrel, and if the barrel be constructed with a patent breech, the view mark shall be also impressed upon the breech.
On arms of the second, fourth, and fifth classes, the provisional proof mark shall be impressed at the breech end of the barrel; the definitive proof mark and view mark shall be impressed upon the barrel above the provisional proof mark; and if the barrel be constructed with a patent breech, or with revolving cylinders or chambers, the view mark shall be also impressed upon the breech, or upon each of the cylinders or chambers with which the barrel is connected, as the case may be.
On all barrels the gauge size of the barrel shall be struck, both at the provisional and at the definitive proof.