Interesting..... none of the W123's here in the States have ABS that I'm aware of. You'll probably have to find someone at a shop that knows that vintage of MB to ask... otherwise maybe some repair manual might give the info. Maybe just a visual inspection will tell you?

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k