Where disagreements arise between the seller and buyer of bituminous coal, in the county of Allegheny, as to the measure of good merchantable coal, put into the wagon, car or cart, at the mouth of the pit, or at any of the wharves in the county of Allegheny, a standard of weight shall be established, of seventy-six pounds avoirdupois to the bushel of merchantable coal.
16 P.S. § 11901