The fill plug is at the drivers’ side of the differential, halfway to the back and just above the upper half in height.
The drain plug is at the passenger side, almost at the rear of the differential near the bottom.
Both bolts are Allen head bolts and are leveled with the differential housing (the bolts do not stick out the housing, but are leveled with it).

If you want, I can send you some marked digital pictures; no problem.

greetingz,

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1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)