Printer's Key - Why Numbers Are Removed Rather Than Added

Why Numbers Are Removed Rather Than Added

With each successive reprint, the publisher needs to instruct the printer to change the impression number, and the theory is that the printer is less likely to make a mistake if they are only removing the lowest number rather than introducing a new number each time. With this arrangement, all the printer has to do is "rub off" the last number in sequence. By changing only the outer number it means that the fewest possible changes are made to the page of characters, which means the smallest possible charge to the publisher. In the days of hot-metal printing, where each character was a metal block, all the printer had to do was to physically pick out the relevant blocks from the "sheet" and then the stack of blocks which would have been laboriously laid out when the page was first set up could be inked up for the reprint. In the case of a Linotype slug, the lowest number could be filed off and the slug reused. In either case, the change was minimal.