The metallic disk that are pictured were used as 'check numbers'. Miners were required to use these numbered disks, each miner was assigned a number when he was employed. Coal loaders were required to place these number disk on the mine cars that they loaded. The cars would be weighed and the 'check number' removed, the coal car then dumped. This was the procedure for recording the amount of tonnage a miner loaded in any given shift of work.

Miners were also required to wear an electrical light on their hard hats. The light source was powered by a battery so when the miner was beginning his shift he was required to go by the 'lamp house' give the attendant his 'check number', [the metallic disk] was then issued a battery pack. This metallic disk was placed on a board and was an indicator who checked out a 'lamp' as well as indicated who was presently in the mine working. After the shift ended the miner returned the battery pack to the lamp house to be recharged and claimed his 'check number metal disk'.

The battery became quite a nuisance. Battery acid would leak from the metal container and decompose clothing as well as cause chemical burns on the miners skin.