The Efficiency Decoration is a medal

Medal

A medal, or medallion, is generally a circular object that has been sculpted, molded, cast, struck, stamped, or some way rendered with an insignia, portrait, or other artistic rendering. A medal may be awarded to a person or organization as a form of recognition for athletic, military, scientific,...

 awarded to New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 military officers. This medal is awarded to officers who have both served for twelve years continuously and been models of efficiency in that time. First awarded in 1931, it was a replacement for the Colonial Auxiliary Forces Officers Decoration, which itself was only 29 years old in 1931, being first awarded in 1902. Recipients of this medal are also given the designation of 'ED' to use after their name.