A number of Whitney U.S. M1816/M1822 muskets were delivered to Commonwealth of Massachusetts under terms of the 1808 Militia Act. Many of these were subsequently altered to percussion at Watertown Arsenal near Boston for the state after 1850. At some time in their career, both flintlock arms and those that had been altered to percussion were adapted to a heavy brass buttplate, with a peculiar knob at its heel. In the process, buttstock was usually narrowed to conform to width of the new buttplate, because many of the muskets encountered with this buttplate bore the inspection mark of Samuel Fuller (SF/V" within a lozenge), these arms were initially considered to have been made for the Massachusetts "Sea Fencible" organizations formed during and after the War of 1812. That appellation, however, has been dismissed, although the exact purpose of the new buttplate and date of its application are not known. These buttplates are usually (but not necessarily) found on Whitney contract muskets and invariably are marked with Massachusetts state ownership mark "MS" on the barrel as well as rack numbers on tang of the buttplate itself. Despite the unknown purpose of these arms, they command a considerable premium over standard flintlock or altered to percussion Whitney muskets.