@seasiderdave and @mustard, yes, I had one of those gun things too! It was kept in a very cheerful 
black cardboard box.
To be fair, it did serve a purpose because injecting yourself with the needles that came with those steel & glass syringes was not what anyone could call insignificant! It could take forever to pluck up the courage to jab one of those needles into yourself without the gun! Those needles were bl**dy thick, not always very sharp, and therefore *always* bl**dy painful ! Even with the gun, about 90% of injections hurt like hell!
I will always remember being amazed, when I started to use plastic syringes with their relatively thin needles, at the relative lack of pain.
I had an uncle who was a GP who supplied me with my first plastic syringes which he got as samples from a sales rep. It was a few years before my own GP was able to prescribe plastic syringes. I was diagnosed in February 1971 (just before my 10th birthday, which I spent in hospital, so I have recently “celebrated” my 40th anniversary!) so I would guess that it must have been about 1978 (?) before I got my first “legitimate” plastic syringes?