Collecting insignia from the Federal Bureau of Investigation since 1999.
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The Questioned Documents Unit examines and compares data appearing on paper and other evidentiary materials. These surface data include handwriting, hand printing, typewriting, printing, erasures, alterations, and obliterations. Impressions in the surface of paper, such as those from indented writing or use of a check writer or dry seal, are also routinely evaluated by Unit examiners, as are shoeprint and tire tread impressions.

In addition to data contained on the surface of documentary evidence, data within paper or other surfaces— watermarks, safety fibers, and other integral features—may be components of document examinations. Unit examiners also match the torn or perforated edges of items such as paper, stamps, or matches.

Other Unit examinations include analyses of typewriter ribbons, photocopiers, facsimiles, graphic arts, and plastic bags. The Unit also maintains a number of databases—the Anonymous Letter File, the Bank Robbery Note File, the National Fraudulent Check File, the Watermark File, and the Shoeprint File.

Source:  Federal Bureau of Investigation