It looks like it's matched to the 1943 proof-dated front/trunnion block part too.

A W- serial number Mk1 gun is also interesting in a strange cock-up sort of way as they are duplicated with Daimler Mk2's.
Is anyone interested in a short resume of how all this came about? It's what you call a total lack of communication between different departments......., each trying to blame the other. So much so, that the paper trail becomes almost indecipherable!