The arms are those of Williams, Penrhyn, co. Carnarvon, Wales.
This mug commemorates the Battle of Lagos, an important British naval victory during the Seven Years' War. In August 1759, the French Mediterranean fleet sailed for Brittany in order to support a planned French invasion of England. Off Lagos, Portugal, they encountered a British fleet under the command of Admiral Edward Boscawen. During the subsequent battle, two French ships, L'Ocean and Le Redoutable, were driven ashore and burnt (as depicted on this mug). In November, the British defeated the French Atlantic fleet at the Battle of Quiberon Bay, permanently dashing the French plans to invade the British Isles.