Sholes and Glidden typewriter length. The redesigned platen also introduced the modern spacing functionality (horizontal and axial movement providing letter and line spacing, respectively). The cylindrical platen became "an indispensable part of every standard [typewriter]". By the end of 1872, the appearance and function of the typewriter had assumed the form that would become standard in the industry and remain largely unchanged for the next century. Although the machine possessed a cylindrical platen and what was essentially a QWERTY keyboard, two design elements that would later become essential were lacking: the ability to write in upper and lowercase letters and "visible" print. Although the
Typewriter original Haas Typewriter Atlases (Pica version) and (Non-Pica version) and the TYPE system developed by Dr. Philip Bouffard, the Royal Canadian Mounted Police's Termatrex Typewriter classification system, and the Interpol's Typewriter classification system, among others. Because of the tolerances of the mechanical parts, slight variation in the alignment of the letters and their uneven wear, each typewriter has an individual "signature" or "fingerprint", which may permit a typewritten document to be traced back to the typewriter on which it was produced. For devices utilizing replaceable components, such as a typeball element, any association may be restricted to a specific element,