Mercedes at one time supplied illustrated parts books with their vehicles. The old ones had black covers and had about 6 x 8 inch pages. Although there were no part numbers listed, the diagrams were valuable when ordering parts. I have seen these books from time to time on Ebay - they might even still be available at the dealers.
Other items that come up occasionally are parts microfiche that the dealers used before going to the EPC electronic parts catalog. These are very handy when doing a restoration.