[Ameliachin]

55+18yo is only 73yo.
But tot NS started much earlier as an old relative in his late 70s had served NS as a policeman.

Think your relative is a Regular, instead of a Police National Servicemen (PNS). You sure his age is correct, and is National Service (NS)?

Full-time National Service (NS) was first introduced in Singapore in 1967. Singapore's full-time National Service policy was extended to the Singapore Police Force in 1975.