A series of identical impressions from the same printing surface. Since the late nineteenth century the number of prints produced has usually been restricted and declared as a 'limited edition'; before this prints were often produced in as many numbers as the process would allow. Modern artists' prints are usually limited to a specified number, anything between 2 and 1,000 or more. Sometimes the quantity is dictated by the process—the plate wears out—but more commonly it is restricted by the artist or publisher, in which case the printing surface is usually destroyed. Editioned prints are usually signed, numbered, and often dated by the artist. An edition of twenty-five will be numbered 1/25, 2/25, etc. These are usually accompanied by a number of proof prints, identical to the edition; those produced for artist are marked 'AP' (artist's proof), those for the printer or publisher 'PP' (printer's proof). A number of working proofs may also be made. 'Bon à tirer' (good to print) proofs provide a standard to guide the printer.