Marine Corps Military Service Numbers
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History Division
Quantico, Virginia


1. Effective 1 July 1905, each enlisted man’s file case was assigned a number and the file case filed numerically. The first, or lowest number assigned was 20,000. The numbers from zero through 19,999 were reserved for Headquarters “general files” correspondence.

2. Previous to 1 July 1905, the enlisted men’s cases were filed alphabetically and when there were two or more cases with the same name, the cases were filed by date of enlistment.

3. Circular Letter 432 of 15 February 1941 directed that beginning on 1 March 1941 the file case numbers became the identification, or serial, number for each enlisted man in the Marine Corps or Marine Corps Reserve. Enlisted men in the service on 28 February 1941 were assigned file (serial) numbers by the Commandant of the Marine Corps and their commanding officers informed. Each number was identical with the file case number then used to identify the man at Marine Corps Headquarters, and remained the same during the man’s entire enlisted service. Each man enlisting in the Corps at the recruiting offices on and after 1 March 1941 was assigned a serial number by the recruiting officer immediately upon completion of the enlistment contract. The Commandant of the Marine Corps assigned blocks of numbers to recruiting districts for the purpose. A man enlisting at a Marine Corps activity other than recruiting, was assigned a serial number by Marine Corps Headquarters upon receipt of the enlistment paper, and the commanding officer of the man concerned was informed of that number. A re-enlisted man was reassigned the same serial number used to identify him during a previous enlistment.

4. In the early 1920’s a number was assigned to each officer’s file case from an alphabetical listing, thus an officer whose name began with “A” was assigned number “01”, etc. The system of filing the cases alphabetically was continued. The number was preceded by an “0” to distinguish it from an enlisted number.

5. On 7 October 1943 the Commandant of the Marine Corps directed by Letter of Instruction 551, that the system of using officers’ file case numbers for identification purposes and on correspondence concerning officers would be instituted, effective immediately. The number was shown immediately following the name of the office wherever it first appears in the correspondence.

6. Identification numbers were first designated service numbers. On 3 May 1950 Marine Corps Memorandum 45-50 was published directing the term “service number” will be used instead of the term “serial number”.

7. On 10 November 1950 the method of filing enlisted cases numerically was converted to a double terminal digit filing system.

8. On 5 June 1953 the method of filing officer cases alphabetically, although identified by a service number, was converted to a triple terminal digit filing system.

9. On 1 January 1972, the social security number replaced the service (serial) number as the primary means of identifying service personnel.

Reference Branch
Marine Corps History Division

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