Mk 111 flying Goggles Help please !

Hi again can anyone help with a few questions on the Mk 111 type flying goggles.

Ref the (R.C.A.F) type Goggles were they only ever dated 1942, or were there other dates of manufacture?

Also i believe some Mk111s were stamped with Air ministry and R.C.A.F markings on the same pair. would this be correct?

I have also seen a pair of Mk111s Stamped with the R.C.A.F. but no date visible any where on the Goggle strap. would anyone else of seen this type of stamp,if so would anyone know a possible year of manufacture ?

As always any help would be appreciated..