[304065]

The mystery unravels a little bit. The original parts manual has cryptic notations like:

M 8 DIN 985-6S verz. SW13

Now, this happens to be a nut that holds the case together.

M 8 is easy enough, metric 8mm.

DIN is of course Deutsche Industrie Normen, and 985-6S is the particular specification called out.

The next part is harder. . but using the online German dictionary we see that "verz." is the abbreviation for "verzinkt" which means "zinc-plated."

And for the final piece of the mystery, SW 13. . . SW means "Schluesselweite" which means "width across flats" or in Maestro-speak, "ATF."

Now back to the specification. DIN 985-6 is a prevailing torque lock nut, FINE thread. . . with a nylon insert.

The trail ends there for now, rabbit just went down the hole. We know that there is NO nylon insert on the original nuts. . . perhaps an older DIN spec that was updated? I don't think even 985 is current, probably replaced by a new ISO standard. . .