Primarily correspondence with related materials including photographs, invoices, newspaper clippings, and dealer catalogs.

Two binders of correspondence labeled "Wessen-Dush Archive" contain original correspondence between Wessen and Joseph F. Dush, an Ohio book collector who acquired much of his collection from Wessen. Volume one includes correspondence with other individuals such as Paul North, Samuel D. Wang, Kenneth Nebenzahl, and with other groups such as the Vermont Historical Society and Yale University Press. Other materials include photographs, biographical information and clippings regarding Wessen, book invoices, and a few item descriptions. Volume two contains correspondence with individuals such as Maxime Schoyer, Roger Butterfield, William H. Vodrey, and Clay Dietrich. Each binder includes a table of contents.

Other correspondence includes Wessen's letters to Ohio collector Arthur Duncan, 1946-1949, and photocopies of his correspondence, 1942-1949, with Jim Scott, an Ohio book scout, bookseller, and librarian. A book of selected correspondence between Wessen and Scott produced by the Northern Ohio Bibliophilic Society is included with the letters.

Related dealer catalogs provide information about Dush's collections. The Ohio Bookhunters catalog contains a memoriam to Wessen.