Hopefully someone on here will be able to give you more specific info from LoC etc. but here is my knowledge of this jumper for what it is.
As I understand it this version of the v-neck army jumper (I am not sure of official nomenclature) was first introduced as part of the late war British jungle green kit. The standard khaki v-neck jumper without reinforcement continued in production for some years after WW2 alongside this green reinforced version and some green jumpers were also made without reinforcement.
These jumpers can be seen being worn in Korea and elsewhere throughout the '50s and '60s, I have three in my collection dated 1945, '50 and '55.
I am not surprised to hear of it's presence in cadet stores in the '70s, I understand they were worn in place of the then new Jersey, Man's, Heavy for a time (indeed if my memory serves correctly a version with a different sizing scheme was made specifically for cadets).
As I understand it the reinforcement and slots for epaulettes were inspired by the WW2 period Indian jumper design shown below.