On all barrels the gauge size of the barrel is struck both at the provisional and at the definitive proof. These gauge marks are readily recognized, as shown in the cuts of the proof marks. Barrels stamped with London marks are not always made in London, for some gunmakers send their barrels to London to be proved, because guns so marked find a readier sale. Barrels with foreign proof marks are exempted, except in case of being marked as of English manufacture. Old muzzle-loaders, if of English manufacture, intended for conversion into other styles of guns, must be subjected to both provisional and definitive proof. It is said to be a fact that the proof marks of both companies are forged and imitated, both in England and in Germany, and many cheap guns so stamped are exported to this country. A cheap gun, with the stamps mentioned, may be looked upon with suspicion as to its really having been in the official proof-houses. The proof marks employed by the inspectors in the U. S. Government armories, and placed on all arms inspected by them, even if made in private armories, are V for viewed, and P for proved, together with the initial letters of the inspector’s name, and are found stamped on each barrel. On many guns of the old model arms will be found, in addition to these marks, the head of an eagle. This is the mark that indicated that the barrels were made at the armory at Harper’s Ferry, when those works were in operation. _Gauge of Gun Barrels._—Guns are gauged by numbers, and these numbers were originally designed to express the number of round balls to the pound that would fit the bore of the barrel. Thus a ten gauge, a ball of which ten made a pound, would fit the bore, etc. Ten and twelve bores are generally used by sportsmen, especially those who use breech-loaders. The twelve, perhaps, is the one most employed. The following list shows the sizes of various gauges, the values of the numbers being those adopted by the English proof companies. The diameters of bores being expressed in decimal thousands of an inch: Number Diameter of of bore Gauge. in inches. 1 1.669 2 1.325 3 1.157 4 1.052 5 .976 6 .919 7 .873 8 .835 9 .803 10 .775 11 .751 12 .729 13 .710 14 .693 15 .677 16 .662 17 .650 18 .637 19 .626 20 .615 21 .605 22 .596 23 .587 24 .579 25 .571 26 .563 27 .556 28 .550 29 .543 30 .537 31 .531 32 .526 33 .520 34 .515 35 .510 36 .506