Under 681.6 is classed information about mechanical details of machines for reproducing material in graphic form, including typewriters and machinery for printing by all the various processes, i.e. relief, intaglio, planographic and screen stencil, machines for the production of printing surfaces, including composing and casting machine: and their components, and devices,for stamping, franking, perforating and otherwise visually identifying documents. This section does not cover the details of printing processes nor the management of printing and publishing, which comes under 655.