Beethoven made notes of ideas, drafts and elaborations for almost all his works. He carefully kept his work papers. Several thousand sheets (70 sketchbook as well as single sheets) still exist. After his death, the sketchbook were torn apart by autograph collectors and souvenir hunters so that hardly any book remained complete.
The sketch collection of the Beethoven-Haus includes books and loose sheets. Many sheets and pages belong to sketchbooks kept in other libraries. The collection thus represents almost the entire sketch corpus. (About sketch research...)
Different traditions are applied for naming the sketchbooks: The name of the previous owner, the place where the book was kept, the library's shelf mark, the time when the book was created, or its content.