PLAINFIELD MACHINE CO., INC.
Middlesex, New Jersey

The serial numbers used by Plainfield Machine followed a consistent pattern throughout production 1962-1978.

Serial numbers were hand stamped one digit at a time and are often not aligned with one another horizontally and/or vertically. The distance between each digit often varies.

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. Serial numbers ran alphabetically then numerically, when 999 was reached the next serial number started at the next letter and again ran 001-999. So far, no carbines have been found that start with the letters I or Q.

Serial numbers were consistently at the front of the left side of the receiver above the stock line. The exception being first half of the G series, which have the serial number on top of the receiver behind the rear sight above the letters PMC. Markings and their location are discussed in detail on the pages devoted to Carbines, Parts, & Markings.

When production reached Z999 the serial numbers started over at 001 without the letter prefix, running numerically through end of production in 1978.

Amongst the first 1500 numerical serial numbers the letter A was sometimes added after the numbers and in at least one instance the letter P was observed instead of the A. Of the 43 carbines recorded between 001 and 1500, 27 have the A, 1 has the P, and 15 have no letter after the numbers. The meaning of this A is not known but of the 27 that have the A, 18 of these are known to have been sold to a law enforcement agency. This practice was discontinued after s/n 1500.

Serial numbers prior to 36000 (letter prefix series included) were stamped within an oval cut out. The oval appears infrequently through 63000 after which it was discontinued.

22 PMC Models (5.7mm Johnson caliber)

Plainfield introduced their 22 PMC models as the Plainfield Machine .30 caliber carbines progressed through the H series. The 22 PMC models were assigned the letter A prefix followed by three numbers. So far, the highest serial number found on the 5.7mm Johnson models has been A356. Instead of Cal. 30 M-1, the receivers are marked .22 PMC M-5.

Enforcer Model

The Plainfield Enforcer model markings and their location are consistent with the markings and locations found on the first Iver Johnson carbines in 1978. The Plainfield Enforcer model was manufactured 1977-1978 during the transition of Plainfield's carbine operations to Iver Johnson. It appears the Enforcer was introduced by Louis Imperato as part of his take over of Plainfield Machine and before the first carbines with the Iver Johnson name.

Serial numbers observed so far have started with the letters PP followed by five numbers. Instead of Cal. 30 M-1 the receivers are marked PP30 M-1. The highest Plainfield Enforcer serial number observed to date has been PP00524.

M-2 Carbines

The Plainfield M-2 Carbines serial numbers are within the M-1 Carbine sequence. The serial numbers do not distinguish an M-1 versus an M-2. The difference is found on the receiver following the caliber marking, where the caliber is followed by M-1 or M-2.

Yearly production varied at different times. Production 1962-1965 was far less than 1966-1975 and diminished 1976-1978. The U.S. Bureau of Alcohol, Tobacco, and Firearms published a yearly list of total rifle and handgun production starting in 1975.

The only rifles manufactured by Plainfield Machine were their models based on the M1 Carbine. Handgun calibers were reported as either revolvers, or pistols in calibers 22, 25, 32, 380, 9mm, and 45. As Plainfield did not manufacture any .32 caliber semi-automatic pistols it is suspected these numbers represent the .30 caliber Enforcer models.

The highest serial number used by Plainfield is not known. The highest recorded to date is 88,847 which is believed to be amongst the final 10,000.