The Efficiency Medal was instituted in 1930 for award to part-time warrant officers, non-commissioned officers and men after twelve years of efficient service on the active list of the Militia or the Territorial Army of the United Kingdom, or of the other Auxiliary Military Forces throughout the British Empire.

At the same time a clasp was instituted for award to holders of the medal upon completion of further periods of six years of efficient service.

[12][13][14] The Efficiency Medal was instituted by Royal Warrant on 23 September 1930, as a long service award for part-time warrant officers, non-commissioned officers and men of the Militia or the Territorial Army of the United Kingdom, and of the Auxiliary Military Forces of the British Dominions, Colonies and Protectorates and India.

At the same time a clasp was instituted, for award to recipients of the medal upon completion of further periods of efficient service.

[1] The medal bears a subsidiary title to denote whether the recipient qualified for its award while serving in the Militia or the Territorial Army or in one of the other Auxiliary Military Forces of the Empire.

[1][15][16] Clasps could initially be awarded to holders of the medal upon completion of eighteen and twenty-four years of efficient service.

[18] A further amendment on 10 May 1946 made part-time officers who served during the Second World War also eligible for the award of the medal and clasp, provided they were serving on the active list of the Territorial Army, the Auxiliary Territorial Service or any Auxiliary Military Force on 2 September 1939 and were embodied or called up for war service.

The suspender is decorated on the obverse with a scroll-pattern bar, inscribed to indicate the military force in which the recipient was serving at the time of qualification for the award.

[14][16] Three suspender scroll bar inscriptions were used on medals awarded to members of part-time forces in the United Kingdom.

[14] Medals awarded to members of the Auxiliary Military Forces of the British Dominions, Colonies and Protectorates and India bore scroll bars inscribed with the names of the respective countries.

The Queen Elizabeth II version, illustrated at the top alongside, is decorated with an embossed Saint Edward's Crown.