What do i know ?
But aren't they the mark for the relief ground into the piston to stop[ the break squeal
if the caliper is mounted on the left side or the right sibde os the axle the relief on the 9 o'clockk side be lower side and 3 o'clck move piston to upper side
That's what is stated in the shop cd
Just my 2 cents

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[B]Mike Y.
00 sl500 sport
88 560 sl (sold)