“Artists Cards Editions and Originals”
Originally there were cards called Artists Trading Cards or ATCs. The mid 1990′s saw trading sessions held in Switzerland where the ATC is said to have originated. ATC cards have to be 2.5 x3.5 inches (the same size as a poker card/baseball card which is slightly larger than a playing card) and they could only be traded.
Lisa Luree changed things in 2004 in order to get around the trading only rule created a new category of cards called Artists Cards Editions and Originals on Ebay enabling anyone to gain easy access to original work.
Anything goes as far as medium or support is concerned, plywood, paper, metal, paint, drawings, collage, 2D or 3D just so long as the dimensions are 2.5 x 3.5 inches.
Since then Ebay has created a category specifically for ACEOs where thousands are listed every day.