10 Dollars Federal Reserve Note, small portrait, with security thread

The security thread in this series was introduced as a direct response to the emergence of high-quality color photocopiers — specifically the Canon Color Laser Copier 500, which the Secret Service had identified by the late 1980s as capable of producing convincing counterfeits of earlier issues. The polyester thread, embedded in the paper and reading "USA TEN" in microprint, was the first major structural security upgrade to U.S. currency since the introduction of fine-line background printing decades earlier.

Notes from the earliest print runs of this series (1990 Federal Reserve Bank of Atlanta and others) occasionally show thread placement variance — the thread sits noticeably closer to one edge than specified. Not an error per se, but documented enough to attract attention from specialists.