10 Crowns - Elizabeth II Lord Mountbatten; Piedfort

Issued to mark the death of Lord Mountbatten, assassinated by an IRA bomb aboard his boat off Mullaghmore, County Sligo, in August 1979. The piedfort format — struck at double the standard planchet thickness — was at this point still a novelty in British commemorative coinage; the Royal Mint had only recently revived the piedfort tradition for collectors, making the 1980 Mountbatten among the earliest modern British piedforts most buyers would have encountered.

The .500 silver alloy, rather than sterling, reflects prevailing cost constraints on commemorative production at the time.