In March 2026, The Royal Mint confirmed a major production error affecting a small batch of 2026 1 oz Silver Britannia coins, where the coins were accidentally struck on base metal blanks instead of .999 fine silver.Coin dealer Chards first discovered the error after noticing weight discrepancies during a routine inspection, finding that a limited run of coins were made of cupronickel (75% copper, 25% nickel).Key Details of the 2026 Cupronickel Error CoinMintage Quantity: The Royal Mint confirmed this was an isolated incident impacting just over 200 coins sent to a trade customer, with a similar quantity caught and quarantined internally. Only 209 coins are confirmed to have made it into the public domain through shipments.Physical Differences: The error coins weigh approximately 28.2 grams, which is noticeably lighter than the genuine 31.1-gram (1 troy ounce) silver version. They also lack the bright, reflective sheen of pure silver.