As far as I am aware, these badges appeared in the late 70s or very early 80s, but were not used by the Regiment for long. When I joined the Regiment in the early 80s they were referred to as "Cadet badges" because that is where they had been relegated.
Very lightweight, they are not a stamped metal badge and are a possibly an early example of a spin cast badge. The one in your photos is is the first damaged one I have seen that shows the star was coated for the final finish.
Curiously, this is the badge that was used in creation of the Regiment's limited edition centennial sword for 1983.