This 38-page pamphlet contains testimony given by Edison in November 1885 and by John F. Ott in August 1888 in a patent interference involving Edison and John Toby Sprague. Technical notes and drawings by Edison and two caveats (preliminary patent applications) for electric meters, filed by Edison in September 1881, also appear in the printed record as exhibits. Included in the testimony by Edison and Ott are discussions of their work on electric meters between 1878 and 1881.
Related interference records can be found in Records of the Patent and Trademark Office (Record Group 241) in the National Archives. Courtesy of Thomas Edison National Historical Park.