This came to my attention: evidently what seems to be [to date and after 60 years] a Unique coin: Great Britain 1967 Record Proof Sixpence. This was said to be found in a bog common 1970 GB Proof Set that was the last of the LSD predecimal series. No special person, no special set and so this was most likely not a "one-off" struck for a special collector by the RM. The best speculation is that this one piece somehow got in with the other 1970 6 pence coins and was inadvertently packaged I can't yet find mention or citation of it anywhere else but will try to see if the Royal Collection has one. Of course I checked my own USD 4.00 (!) 1970 set and the sixpence was, naturally, a 1970 specimen. I do have an uncirculated 1970 halfpenny struck in iron though... Anyway, here is the 1967 piece and then my sorry 1970 coin of same design:
