50 Pence - Elizabeth II Kew Gardens, Gold Piedfort

The standard cupro-nickel Kew Gardens 50p, issued the same year to mark the 250th anniversary of the gardens' founding, became the rarest circulating 50p in modern British coinage by mintage — just 210,000 struck for general circulation. The gold piedfort version occupies an entirely different category: a collector piece from the outset, double the thickness of a standard coin, and produced in tiny numbers relative to even the commemorative silver editions.

Piedfort production at the Royal Mint traces back to medieval France, where doubled flans were struck as presentation pieces or official weight references. The modern British revival began in earnest in the early 1980s.