This is an example of a rare U.S. Springfield Model 1816 flintlock musket altered to Jesse S. Butterfield's patented pellet primer mechanism. These Pennsylvania contract Butterfield alteration muskets are described on pages 84-85 of George D. Moller's book "American Military Shoulder Arms, Volume III", and this musket is pictured on the bottom of page 84. Moller notes that Butterfield was contracted to convert 1,000 muskets on July 2, 1861, for $4.00 each. He made two deliveries of 100 muskets each on September 2 and November 6, 1861. This conversion consisted of installing a new bolster on the end of the barrel. The main conversion consisted of installing a new pellet primer mechanism on the side of the lock. This mechanism had a tube located on the underside that held the "wafer-primer." Each time the hammer was cocked, it would feed one primer up to a sliding bar located under the hammer that would position it over the nipple. The lock is marked "SPRING/FIELD/1837" vertically behind the hammer and "BUTTERFIELD'S/PATENT DEC 11, 1855/PHILADA" ahead of the hammer. The barrel markings were removed during the conversion. Oval script "ET" and "EB" inspection cartouches marked on the left stock flat. Serial number "90" is marked on the middle barrel band, underbelly of the stock ahead of the trigger guard, inside of the left side plate, left stock flat, inside the lock and its internal components, and inside of the buttplate. "US" marked buttplate tang. Single letter "S" marked on various components. "GDM" (George D. Moller) collection initials marked at the toe of the stock. Includes "U.S." marked socket bayonet and period leather sling with initials "MB" carved into it. Provenance: The George Moller Collection