Hi chaps, not been on for years but still shooting now and again.

Decided to strip down my old Meteor (T prefix MK I) and I'm not sure if something is missing from the piston head assembly. The gun is very original AFAIK.

Please see pic - the piston head fits into a keyhole type aperture on the end of the piston but is loose on there when central - is there supposed to be a circlip or something or another washer to make it a tighter fit??