The rare Butterfield revolvers were manufactured by Jesse Butterfield of Philadelphia, Pennsylvania, in 1862. They are considered by collectors to be secondary U.S. martial handgun since they were manufactured in anticipation of an unrealized government contract. Because no contract was awarded, production was limited to only about 640 revolvers. It is equipped with a special disc priming device loaded by loosening a thumb-screw in front of the trigger guard. The top strap is marked "BUTTERFIELD'S/PATENT DEC 11. 1855/PHILADA".