Restrikes are later impressions that have not been authorized by the artist or the artist's heirs. While some restrikes are of good appearance, the excessive printing of the matrix tends to wear it out and many restrikes are only ghostly images of what the print is supposed to be. In the case of images that may be intrinsically valuable (i.e. compositions by Rembrandt), the worn-out copper plate is often reworked several centuries later so that, while the restrike may be said to have come from the original plate, there is hardly anything left of the original work on the plate, even the plate's signature often being re-etched by someone else.