I'll second that Rog, i'd be interested to know introduction / manufacture dates too.
Re the No53 I've got copies of DDE manufacturing final approval drawings dated early 44 for the installation of the 53 on both the P14 and No4(T). Now there's an interesting mount to reproduce!
Cheers,
Simon.
BTW Not sure how elevation would be catered for in those PH mounts but the windage was a simple matter of opposing screws.