There were many sizes of domestic (for home use) coal. If memory serves me right, from smallest to largest was: rice, pea, nut, chestnut, stove, egg and lump. Most domestic coal was branded at the mine by either tossing little paper or aluminum tags into the train car as the coal was loaded or by spraying paint on the coal as it loaded. "Great Heart" coal had little paper hearts, "Green Mark" coal had globs of green paint all through it. Coal dealers played lots of games, they would buy "generic" coal and toss tags that they had filched out of previous loads, they'd spray their own paint. If you asked for a certain kind of coal, they'd come up with a way to convince you that that's what you were getting. More than you ever wanted to know.