This book covers the period April 1902-January 1908, with most of the letters dating from 1902-1904. The letters consist primarily of instructions, sometimes accompanied by drawings, from Edison to draftsman William Simpkin regarding the plant and machinery at Dunderland. Some of Edison's comments pertain to the receipt of Dunderland briquettes at West Orange and to plant operations at the Edison Portland Cement Co. in Stewartsville, New Jersey. There are also letters concerning drawings from the New Jersey and Pennsylvania Concentrating Works.

The flyleaf is inscribed "Aug 12, 1902 - Jan 29, 1908  Dunderland Iron Ore Letters." The spine is stamped "Letters." The book contains 995 numbered pages. Pages 180-925 and 963-995 are blank; pages 100 and 102 have been removed from the book. Approximately 40 percent of the documents have been selected. The unselected items are primarily duplicates of letters that appear in the Standard Construction Corporation, Ltd., Files, General Letterbooks Series, and Document File Series.