Wikipedia
V-Disc ( "V" for Victory) was a morale-boosting initiative involving the production of several series of recordings during the World War II era by special arrangement between the United States government and various private U.S. record companies. The records were produced for the use of United States military personnel overseas. Many popular singers, big bands and orchestras of the era recorded special V-Disc records. These 12-inch, vinyl 78 rpm gramophone recordings were created for the Army between October 1943 and May 1949. Navy discs were released between July 1944 and September 1945. Twelve-inch discs were used because, when 136 grooves per inch were cut, they could hold up to six and a half minutes of music. Not all releases were pressed of vinyl; many were of the much less durable shellac compound used for standard 78 RPM records of the day.
Army V-discs were issued in series A-Z, AA-ZZ and AAA-FFF. Navy V-discs were issued in series A-N.