Different forms of the tally system were used in many of the larger industrial organisations, involving pairs of tallies, usually stamped with a unique number and with an off-centre hole so that they could be hung up in number sequence when not in use. The best known were issued in conjunction with miner's lamps and enabled the mine office to know at all times which men were underground, an essential function in the event of an accident. Similar systems were used to ensure that valuable tools were returned to stores and that workers received their wages once and once only.