When I visited the Vacor factory in Guadalajara some years ago, their "sorters" sat on stools at a high rectangular table and pulled marbles (same style) out of a 50 gallon drum after they had cooled down for couple days. They threw the damaged ones into another smaller barrel and put the good ones in boxes to send to the other part of the factory that did the packaging into bags. They had 3-4 quonset style buildings, each about football field size where they did their work. They would not let me take pictures inside the factory.