<P> 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, rather than to the typewriter as a whole . </P> <P> The earliest reference in fictional literature to the potential identification of a typewriter as having produced a document was by Sir Arthur Conan Doyle who wrote "A Case of Identity" in 1891 . In non-fiction, the first document examiner to describe how a typewriter might be identified was William E. Hagan who wrote, in 1894, "All typewriter machines, even when using the same kind of type, become more or less peculiar by use as to the work done by them". Other early discussions of the topic were provided by A.S. Osborn in his 1908 treatise, Typewriting as Evidence, and again in his 1929 textbook, Questioned Documents . A modern description of the examination procedure is laid out in ASTM Standard E2494 - 08 (Standard Guide for Examination of Typewritten Items). </P> <P> Typewriter examination was used in the Leopold and Loeb and Alger Hiss cases . In the Eastern Bloc, typewriters (together with printing presses, copy machines, and later computer printers) were a controlled technology, with secret police in charge of maintaining files of the typewriters and their owners . In the Soviet Union, the First Department of each organization sent data on organization's typewriters to the KGB . This posed a significant risk for dissidents and samizdat authors . In Romania, according to State Council Decree No. 98 of March 28, 1983, owning a typewriter, both by businesses or by private persons, was subject to an approval given by the local police authorities . People previously convicted of any crime or those who because of their behaviour were considered to be "a danger to public order or to the security of the state" were refused approval . In addition, once a year, typewriter owners had to take the typewriter to the local police station, where they would be asked to type down a sample of all the typewriter's characters . It was also forbidden to borrow, lend, or repair typewriters other than at the places that had been authorized by the police . </P> <P> The ribbon can be read vertically, although only if it has not been typed over more than once . This can be very hard to do as it does not include spaces, but can be done, giving every typewriter a "memory". </P>

Why was there a need for the typewriter