This folder contains correspondence and other documents relating to the technical and commercial development of phonographs. Among the documents for 1910 are items pertaining to the development of diamond reproducing points, inexpensive phonographs for foreign markets, and disc phonographs. Also included are a general report on the American phonograph market; a comparative report of general expenses for the National Phonograph Co. for the period June 1909-June 1910; and letters to Edison about the phonograph, to which he responded with marginal comments. Some of the letters are by Frank L. Dyer, president of the National Phonograph Co.

Approximately 50 percent of the documents have been selected. The items not selected include routine inquiries, letters of transmittal and acknowledgment, and items that duplicate information in selected material.