A signed print is one signed, in pencil or ink, by the artist and/or engraver of the print. A print is said to be signed in the plate if the artist’s signature is incorporated into the matrix and so appears as part of the printed image. Proof prints were originally signed as “proof” that the impression met the artist’s expectation. Later proof prints were signed in order to add commercial value to these impressions. In the late nineteenth century, in response to the development of photomechanical reproduction techniques, fine arts prints were signed by the artists in order to distinguish between original prints and reproductions. Seymour Haden and James McNeil Whistler are usually credited with introducing this practice in the 1880s.