2023 Britannia Silver Proof 5 oz UK Coin. 999 With OGP Box & COA – Only 420! Only 420 Britannia silver coins are available in this Limited Edition Presentation. Struck in five ounces of 999 fine silver to Proof quality. The first commemorative Proof Britannia coin to feature the portrait of His Majesty King Charles III. Artist Jonathan Olliffe’s design features seahorses, inspired by royal carriages used during processions. Explore the story of Britannia and her role as a symbol of Britain in the accompanying booklet. Weight: 5 oz (156.30 g). Reverse Designer: Jonathan Olliffe. Obverse Designer: Martin Jennings. Packaging: OGP Box & COA.