The one dated item in this file is a March 1886 letter written by Charles Batchelor in his capacity as general manager of the Edison Machine Works. The letter, which is addressed to Edison, concerns a new armature design. Also included is a note, probably from 1880, to Francis R. Upton, manager of the Edison lamp factory, regarding a vacuum pump. In addition, there is an unsigned drawing, probably by Edison, of an arc light.

Courtesy of the Henry Ford Museum and Greenfield Village Research Center.