The available guns were truly a hodge-podge. In the beginning the ordnance consisted of whatever could be "liberated" before the British Army came along and removed them - obsolete cannon from coast batteries, hand-me-down guns of volunteer companies and ships cannon. The motley collection consisted of three-pounder to 24-pounder guns, with the larger calibers most numerous. As a result of this imbalance, and because it was inevitable that this small stock of ordnance would be insufficient, gunfounding was begun in various places. The first to be produced were small one- and two-pounder swivel guns for naval use, but once the techniques had been mastered larger weapons were made. In 1776 some sixty 12-pounders and 18-pounders were cast in Pennsylvania, and shortly afterwards a standardized four-pounder light field gun was put into production. This is where the genius of Henry Knox came to the fore. Instead of having cannon of all sorts and dimensions cast all over the place, he pressed for the concentration of manufacturing effort in one place, where it could be controlled, supervised, and simplified, and he selected Springfield, Mass., as the gunmaking centre. Knox was confident that the British commanders would neither appreciate the significance of Springfield nor, if they did, be capable of carrying out an operation against the town. American-manufactured guns were largely copies of British standard models, since these were the easiest to obtain for the preparation of patterns. A few were constructed on the lines advocated by John Muller, who was the Professor of Artillery and Fortification at the Royal Academy, Woolwich. His book, "A Treatise of Artillery," had been published in 1756 and was the standard text of the day, and a pirate copy was published in Philadelphia in 1779, which became the handbook of the American artillerymen. In this book Muller had published plans of cannon based on sundry theories of his own, and as a result the few cannon which were ever built to Muller's ideas were made in America. You can tell an American cast tube by looking for a liberty cap on a pole and a sunburst design cast into the metal. The letters "U.S." or "U.C." for United Colonies also appear on some guns.