It's a good while since glass syringes have been used!
I can remember my Dad sterilising them when I was a child, but they were out of general use by the time I started working in labs in '75.
The aluminium canisters were essential to the sterilising process - the syringes were placed inside them with the screw-tops fitted only loosely, so the steam would penetrate inside them inside the autoclave.
(a sort of pressure cooker). When it was safe to open the autoclave, the tops were tightened, keeping the syringe sterile inside.