This notebook was used by William Walter Dinwiddie and his assistant Henry E. Thayer during January-July 1919 for notes on the production of blanks for disc records. There is one additional entry from October 1919. Edison's supervision of the work is indicated by Dinwiddie's references to his suggestions and comments. The experiments are numbered from D401 through D467. The entries describe the methods used in the manufacture and preparation of the blanks, particularly the baking process, and contain remarks about the results of the experiments. Several indicate that a particular print sounded good or bad to Edison or that "Mr. E can't hear surface." Also included are lists of clays, along with remarks about their characteristics, sources of supply, and prices. The notes indicate that W. R. Simpson assisted Dinwiddie in some of the work and that Charles T. Dally used some of the same materials as Dinwiddie in his experiments. Pasted into the book is a one-page note by Edison pertaining to a patent on a shellac substitute that he wanted Dinwiddie to try. The front cover is labeled "Dinwiddie D-401 -" and "Disc." The pages are unnumbered. Approximately 100 pages have been used. Courtesy of Thomas Edison National Historical Park.