Legend tells us that 18th century Royal Navy press gangs (recruitment officers) used to hide a signing-up bounty (the 'King's Shilling') in the 'free pints' that they offered to unsuspecting sailors in waterside taverns. Drinking the beer was deemed to be acceptance of the money, and commitment to recruitment in the King's service (harsh discipline and dreadful food!).
The glass-bottomed tankard was said to have been invented so that men would spot the trick before it was too late. In commemoration, our hefty, one-pint, Sheffield pewter tankard has a double glass bottom with a genuine old shilling sandwiched between. The King's Shilling story is engraved on one side of the tankard.