This is an excellent, very rare example of an early post WWII M3-AC (basic aircraft version MG) originally manufactured by Springfield Armory (the U.S. Government facility) in 1952. This is noted as being only "1 of 1470" receivers actually manufactured by Springfield Armory circa 1951/52.
This M3-AC version is fully working Dry firing and can be field stripped down and has been sympathetically deactivated.
This very fine example with 98% of its current parkerized finish overall with edge and high spot wear, with some signs of limited firing. The markings are clear and sharp.
Just an excellent example of a very rare original U.S. Government Springfield Armory M3-AC machine gun