Thanks M,
I found this response to a question re: 230SL wiper motor :
W113SL
Inactive
USA, FL, Naples
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« Reply #1 on: October 04, 2011, 20:52:46 »
Wiper motors are natural steel, unpainted . I suspect they were cad or zinc plated when new but not yellow dichromated. You can strip off the old paint and clear coat it to be correct.
Pete Lesler
National Concours Committee Chair
MBCA