(in the UK) Distinguished Service Medal, a medal for distinguished service at sea, instituted in 1914.
（英国海军的）服役优异勋章（始于1914年）
Definition of DSM in US English:
DSM
abbreviation
Distinguished Service Medal, (in the US) a military decoration for exceptionally meritorious performance of a duty of great responsibility during wartime or (in the UK) a medal for distinguished service at sea.