Nutty,
I believe that one had to be serving at the time of the change, which I believe was 1975. I was demobbed March 65.
As Shack37 has indicated, the rules for Boys & Apps were convoluted.
Our engagement didn't start until our 18th birthday, but pensionable service, if you stayed in that long, was counted from 17 years and 6 months.
So anyone that did their 22 received at least 22.5 years pension!
I tend to 'round out' my service and say that I served 13 years, but it was actually 12 years 10 months, less 5 days
