Miners would call these ‘tags’, ‘checks’ or more locally ‘motties’. Every miner had one. It had the name of the coal mine he worked at and his own personal number stamped on it.
Just before a miner went to work underground in the pit, his token would be hung from a large numbered peg board.
This was a safety check to show exactly who was underground at any given time. In cases of emergency, it was important to know how many miners were underground as quickly as possible.