I don't recall touching the rear brakes. At most I changed the main pads.

Easiest thing is to pull a rear rotor of a 123 or 126 so you can see the star wheel. There's a good picture in the Haynes W123 manual. You can also check mb.braingears.com . Maybe this shortcut will work - http://mb.braingears.com/126_DISC1/program/Chassis/42-0540.pdf

Sixto