Ala. Code § 25-9-41: Checking Systems.

Each mine shall have a check-in and check-out system that will provide positive identification upon the person of every individual underground. An accurate record of the men in the mine, which shall consist of a written record, a check board or a time clock record, shall be kept on the surface in a place that will not be affected in the event of an explosion. Said record shall bear a number identical to the identification check carried by the person underground.