These are artworks which not equal in quality to the general edition that may have minor flaws. These usually aren't signed and are canceled in some way, such as a hole in a corner or a stamp indicating they are not for sale. These artworks are used by sales people to show to potential clients. They are often marked with the letters "HC."
These prints are outside the edition but are the same as the edition and are used as gifts or payments to those involved in the production of the edition.
Prints marked by an artist for business use only (H/C). Literally “not for trade.