This series contains the indexes used to identify the Long Number by which the First World War army officers service records are organised in WO 339. The main series of officers' service records was destroyed by bombing in 1940 and what remains is a supplementary series. In some cases, the supplementary file had been destroyed by clerks before 1940, and so no service record exists any longer. Further advice on these records can be found in this leaflet: British Army Officers' Records: First World War 1914-1948 .
A single index volume from the earlier pre-1857 Long Number system survives (Long Numbers up to around 99,000) and covers papers registered after 1870. Long Numbers allocated to Royal Army Medical Corps officers were not included in the reorganised system; possibly the survival of a practice when the Army Medical Department operated a separate registry system.
Entries for some temporary commissioned officers can also be found in the indexes, although their files were transferred to a 'vowel' system in or around 1915 and cross-references to this system are included in the registers.
The indexes also provide cross references to the subsequent P (Personal) Numbers if the officer continued in service after April 1922 when the Long Number series was replaced.