While the numbering of individual impressions (prints) can be found as early as the late nineteenth century, it did not become standard practice until the mid-1960s. Before steel facing and other ways of preserving plates for longer print runs, the order in which the edition was printed was important. Today, all limited edition prints should be numbered, and because of advancements in technology and a master printer's ability to print reciprocal, identical images, the numbering sequence is no longer intended to reflect the order of printing. Numbering is transcribed as a fraction with the top number signifying the number of that particular print and the bottom number representing the total number of prints in the edition. The edition number does not include proofs, but only the total number of prints in the numbered edition.