It's Crystal Blue Stripe, not Sea and Sand, (which is a later design of a frothy yellow with a band of Tiger around the middle).
Crystal Blue Stripe is the name given to this design, but later on. It didn't have a name at the beginning. It has been in production since MH's time there, and this is a fairly common shape to find. I don't actually know how long it was in production for - it might still be being made.
To date one, I go by the sort of mark on the base and have a look at how wide and how well the flange is made. Wide flanges didn't really appear at Mdina until after the Boffo's arrived, it was them who taught MH how to do these rather than buttons.
Given your flange is quite big and wide, I think it's more likely to be from well into the '70s or even later.
I can't actually see the script, so I don't know if it's done in a fine line or of it's a thicker version where the drill bit goes sideways and makes the mark all fuzzy.
