Alan Turing 50p (2022)

As a collector-only issue, the Alan Turing 50p is priced on condition and packaging rather than circulation wear. A coin still sealed in the Royal Mint pack fetches more than a loose one or one moved into a capsule or another firm's card. Scratches, spots and a creased or opened pack lower its value. The silver, silver piedfort and gold proofs of the Turing design had fixed edition limits and form a separate market.

The Alan Turing 50p was not issued for circulation, so it has no rarity rank.

Look for a large cogwheel over a dense grid of letters that fills the whole reverse, with ALAN TURING alongside the cog. Reading the grid closely turns up the hidden words, including GEARS GRIN THAN and ONLY A FORETASTE. On the obverse is Queen Elizabeth II with the year 2022. It was never put into circulation, so the coin is found in collections rather than in change.

Alan Turing is regarded as a father of modern computing, and his codebreaking work in the Second World War was central to deciphering Nazi messages. After his posthumous royal pardon in 2013 he also became a figurehead for gay rights, and the further pardons that followed became known as Turing's Law. The Royal Mint issued this 50p in 2022 as the sixth and final 50p of its Innovation in Science series and the first UK coin to commemorate him. Designers Matt Dent and Christian Davies placed a cogwheel in the foreground, a nod to the Bombe, the code-breaking machine Turing developed, against a background of Enigma-style letters that covers the coin, with the inscription ALAN TURING. The letters hide three codes. GEARS GRIN THAN is the three-word location address for Cambridge University, where Turing studied. Another spells out ONLY A FORETASTE OF WHAT'S TO COME, words Turing gave to The Times in June 1949. The third is the designers' initials, CD and MD.

In the Innovation in Science set it was issued in 2022 together with the Alexander Graham Bell £2, and the Edward Jenner £2 followed in 2023.