Here is one reference I found;
121.941 M 121 B.XII 1 0019
121.942 M 121 B.XIII 1 0019
The single number refers to "Sector" the "0019" is Microfiche.
Brooklyn Motoren Werke (608-455-7441) has a listing for parts for that motor designation, try a phone call to see if they can provide the detail.
One other item I was able to find - 1988 CC, 59 KW (80PS)
A seller on ebay had valves listed for that motor designation, and a car listing of 200. But it was not clear if that was the correct car and engine combination.
