The chop is customarily a symbol that holds particular meaning for the printmaker or owner of the commercial press.
This is an embossed mark that designates the print studio where the print was produced. I wrote previously about the creation my chop. Professional print studios usually use a chop. Independent artist /printmakers frequently do not. The chop is usually pressed into the lower margin of each print, near the edge. In the case of a bleed print (where the image bleeds off the edge of the paper) the chop might be placed in the image itself, although obviously the artist is going to have a say in this. The alternative is a blind stamp on the verso with a light ink that will not show through.