Serial numbers started with the Millville Ordnance and H&S carbines were continued into the Plainfield carbines and consisted of a letter followed by three numbers. The distance between each digit often varies. Serial numbers were hand stamped one digit at a time and are often not aligned with one another horizontally and/or vertically. The serial numbers used by Plainfield Machine followed a consistent pattern throughout production 1962-1978.
* Production may have started at A001 or A100 Carbines are presented in four different sections, each consisting of one or more pages. Post WWII Commercially Manufactured M1 Carbines (U.S.A.)
