The Imperial Service Order was established by King Edward VII in August 1902. It was awarded on retirement to the administration and clerical staff of the Civil Service throughout the British Empire for long and meritorious service. Normally a person must have served for 25 years to become eligible, but this might be shortened to 16 years for those serving in unsanitary locations. There is one class: Companion. Both men and women are eligible, and recipients of this order are entitled to use the post-nominal letters 'ISO'.