Lou,
I can't help you with what it was used with but, somewhere I believe I have a diagram for it.
The markings are interesting;
The 'A' suffixing the Mark number denotes a fuze similar to the previous converted Mark, but of new manufacture.
This would suggest the Mark VI was in fact a conversion of a Mark III and the amendations were of such a number or nature to warrant a new mark number. Normally a fuze subject to minor conversions would be denoted by having an asterisk stamped after the Mark number.
Thus your fuze is possibly a fresh manufactured Mark III incorporating all the updates from scratch, but caled a Mark IVA.
If it was new manufacture, it does beg the question why has the III been overstamped? The only thing I can think of is that maybe the nose cones had been manufactured and stamped prior to the contract being altered.
CC is the maker's mark, if I was sure it was a British manufactured fuze I would opt for Carron & Co of Falkirk Scotland who although were primarily ferrrous founders also had a Brass and Aluminium capacity. Digressing slightly, many British Pillar (post) boxes were cast by Carron.
My doubt as to the nationality of manufacture is the slash after the CC. This, if followed by a C, would denote Canadian manufacture.
Another possibility is the Chrysler Corporation.
Are there any other markings?
Regards
TimG.