Service Number
From Navy.ca Wiki
A Service Number (SN for short) is a unique identifier assigned to every member of the Canadian Forces. It consisted of one letter and eight digits.
Previously, members were identified in departmental records by their Social Insurance Number; this use of SINs was contrary to Government of Canada regulation. SNs were introduced in the early 1990s to replace the use of the SIN.
Within the Canadian Forces, SINs are only used in the military pay systems, CCPS and RPSR.