Finally, after reading through copious amounts of records I believe I have finally resolved one the long standing issues about the silver ARP badge. The C- and D-dated badges have a maker mark of "J.C." in a lozenge with snipped top corners.
Across the web and also on some silversmith websites this is incorrectly identified as Jacques Cartier (which is utter toshas their hallmark looks nothing like those on the ARP badge).
I recently got hold of a file from the National Archives which detailed that 'J.C.' was in fact a Royal Mint mark. I then emailed the Goldsmiths' library in London and they sent through the details of the mark being registered to a certain John Herbert McCutcheon Craig (first and last initial 'J.C.'). He was the Deputy Master and Comptroller of the Royal Mint from 1938.
On the silver ARP badges that were manufactured in 1936 and 1937 the hallmark is 'R.J.' which was for Sir Robert Arthur Johnson the former Deputy Master and Comptroller of the Royal Mint who died in January 1938.
News about interesting insignia, ARP related info and period photos that turn up.