Metal tankards often come with a glass bottom. The legend is that the glass bottomed tankard was developed as a way of refusing the King's shilling, i.e. conscription into the British army or navy. The drinker could see the coin in the bottom of the glass and refuse the drink, thereby avoiding conscription. However, this is likely to be a myth, for the Navy could press by force, rendering deception unnecessary.
In a bar fight, the first punch was thrown while the recipient had the tankard raised to his mouth; another legend has it that the glass bottom was implemented so as to see the attack coming.
A further story is that the glass bottom merely allowed the drinker to judge the clarity of their drink while forgoing the expense of a fragile pint glass.
Covered tankards fell out of fashion in 19th century England resulting in a number of them being converted to other roles such as jugs.
Modern metal tankards are often engraved to commemorate some occasion.
In previous centuries, the pewter used to make tankards often contained lead, which exposed the drinker to medical effects, ranging from heavy metal poisoning to gout. Pewter is now widely lead-free.