Briefly...

Many casinos would contract with low-security prisons, more likely with a 3rd-party service to have prisoners sort and box cards for resale at the casinos and also at various discount stores.

This method, as of late, has stopped because of poor quality control. Too many times the reassembled decks had missing or duplicated cards. This was a function of the casinos just gathering up the used decks and dumping them into a large box fr transport to 3rd party, without the empty boxes and no jokers.

At the sorting location, sorters would grab hand fulls of cards, face them and place the stacks into a corner cropper device, cutting the corners of 100's of cards at a time. If a card was not faced right, it was cut wrong, but still used.

After the cutting, only then would the cards be sorted and if two of a same card was used, or one stuck to another, or was omitted, oh well. And, the corner cutting machine was hand fed, meaning that the cuts were not all uniform.

For decks headed to retail venues, generic boxes were used. Enough of that, but the days of getting nice used cards from a casino are long gone.