There are some subscription services that offer the full part number look up - it used to be called the EPC (electronic parts catalog) provided through Mercedes. I have not used these so you may get some hits to your forum post with further direction.
The associated parts book to match the number you posted would be 10142. It would also be labeled as Catalog B, inside "as per January 1968". They do come up from time to time, and are usually not a cheap investment.
