This letterbook covers the period June-August 1891. Most of the letters are by Alfred O. Tate. There is also correspondence by Edison and Thomas Maguire. Many of the letters pertain to the manufacture of phonographs and cylinder recordings and to Edison's relations with the North American Phonograph Co. and the Edison United Phonograph Co. There are also numerous letters relating to the business of the New Jersey & Pennsylvania Concentrating Works, including the leasing of mining properties and production problems at the Ogden ore milling plant. Other correspondence deals with the Edison-Lalande battery and strategies for marketing the battery in Europe. There are some documents relating to kinetograph experiments, the Edison phonoplex system, electric lighting and power, and the mimeograph. Beginning on page 381 is a letter by Edison listing recent improvements in the incandescent lamp. Included also are several letters concerning Edison's personal finances and the investments of his father, Samuel. The spine is labeled "From June 13, 1891 to Aug 24, 1891 No. ." The book contains 697 numbered pages and an index. Approximately 25 percent of the book has been selected.