[This note covers all of the Caveats in Record Group 241.]
Until 1910 the U.S. Patent Office permitted an inventor to file caveats, which were official notices regarding work in progress. Caveats were valid for one year and were renewable for an annual fee. If another inventor subsequently filed an application for a similar invention, the Patent Office notified the original inventor. These Edison caveats, which cover the years 1872-1891, relate to telegraphy, electric pens, telephones, electric light and power, phonographs, iron ore separation, and other topics. They contain detailed notes, drawings, and specifications regarding each invention.
A draft of this caveat, in Edison's hand, can be found in Letterbook, LB-001, pages 35-67. Courtesy of the National Archives.