Several variations and improvements were made upon the Adams, which was manufactured in Europe and briefly in the United States under license. The majority of British-made Adams guns seem to have been in 54 bore (approximately .44 caliber), but several smaller and at least one larger bore were also offered. In 1857 the U.S. government purchased 100 revolvers in .36 caliber and another 500 from the Adams-licensed Massachusetts Arms Company. The 100 British-made guns were issued to the U.S. Army with the rest held in storage until issued at the outbreak of the U.S. Civil War. In addition Adams revolvers were purchased from the London Armoury prior to and during the war by individual states and the U.S. and Confederate governments.