For officers the AFPS75 pension has always kicked in at 16 years reckonable service. So if you were serving from age 21 this would equate to age 37. In the RAF the ToS provided an exit point at age 38 but you could PVR earlier and still qualify for pension (albeit at the PVR abated rate). I understand that the Army ToS was 16/37 but not sure what the RN used.