52 Pa. Stat. § 672.3
Every owner, operator, lessor, lessee or general contractor engaged in the mining of anthracite coal or any president, director, general manager, superintendent or other person in charge of, or having supervision over, any anthracite coal mine or mining operation in this Commonwealth shall be and is hereby required (1) to designate within a period of six months from the passage of this act, and to keep designated by number, each and every pillar of anthracite coal beneath the surface still remaining in place at the time this act goes into effect, and all pillars thereafter created, the number of each pillar to be placed in a conspicuous position with white paint or some other equally durable and visible substance; and (2) to designate or cause to be designated by numerals of convenient and legible size, upon all maps or plans mentioned in section 2 of this act with the space on each map or plan designating any pillar of coal, the number of such pillar.
52 P.S. § 672.3