Distinguished Service MedalDistinguished Service Medal Full size medal Unmounted with 15cm ribbon as required for swing mounting. Miniature size medal Unmounted with 10cm ribbon as required for swing mounting. The Distinguished Service Medal (DSM) was a military decoration awarded until 1993 to personnel of the Royal Navy and members of the other services, and formerly to personnel of other Commonwealth countries, up to and including the rank of Chief Petty Officer, for bravery