1. Introduction.  It was not until February 28, 1918, that the first service number was issued to an enlisted man.  Master Sergeant Arthur B. CREAN holds the unique distinction of receiving Army service number 1.  Officers did not receive service numbers until June 1921.  General Pershing, who was then Chief of Staff, received the number O-1.

2. Periods of issuance for service numbers.  Tables attached as Fig. A-1 contain service number series broken down by issuance periods as short as feasible.  When not feasible to break down by short periods, an effort was made to break down series into periods closely corresponding with those covered by specific records groups, some of which were lost in the July 1973 NPRC fire.  For easy reading, numbers are entered in the "Series" column in the
conventional style with a comma between each three digits starting from the right, however, no relationship between this and the way numbers are encountered in correspondence and on military records is intended.  The most prevalent style in which numbers are encountered in correspondence and records is depicted by the following:
 
 

Many groups of numbers issued out of their normal sequence may be inaccurately or incompletely accounted for in this brief table.  These are numbers, for instance, which were surplus due to an over estimate of needs in the area or category for which initially set aside.  In these cases, however, the tables indicate general trends.  "EM" means enlisted personnel (including draftees), men as well as women.  "Ofcr" means officers and includes warrant officers.

3. Service number prefixes and suffixes.  The majority of prefixes and suffixes were for Air Force and Army.  None are known to have been used with Coast Guard service numbers.  For Marine Corps, only "O" (Officer) and "W" (Women) were used.  Navy used "W."  In addition, beginning in December 1965, Navy enlisted personnel received six digit numbers with a letter prefix.  The first series used was "B10 00 00 thru B99 99 99."  When all these were used, succeeding letters of the alphabet were assigned with the same series of
numbers, however, letters which may have resulted in confusion with other letters or with other identification numbers were not used.  The various prefixes and suffixes assigned are contained in Fig. A-2.