Re: Plainfield Machine M-1 Carbine???????s
I am not sure what I can tell you that you don't already know. Plainfield was the successor to Milliville Ordnance Co., Millville, NJ, and was also in business in New Jersey, first in Dunellen, then in Middlesex, from about 1967 until it was bought out by IJ in 1975. Most of their carbines were copies of the GI M1 Carbine, but they also made full auto (M2 copies) for LE and foreign sales, and had a under type folding stock that was like that on the German MP.38 SMG and was better than the GI carbine side folding stock. Most of their parts were GI surplus, but the receivers were cast. They had at least some barrels made by a subcontrator who turned down surplus M1903 barrels.
IIRC, quality control was not high, and buyers experienced a lot of problems. Ruth, in War Baby Comes Home says their record keeping was poor and that there is no good record of serial numbers or of total production figures.