A proof made during the creative process by the artist to check on the progress of the work. See proof, artist's proof, edition proof.
A proof that varies from the edition either in color, size, drawing, printing order, etc. these proofs are usually pulled before the artist has arrived at the final decision for the edition. These prints are usually unique impressions which may be retained by the artist and are not numbered in any manner.
a pre-cursor to a limited edition series, thse prints are pulled so that the artist may refine and perfect the prints to the final state desired. These are usually unsigned.