Once I've seen a remanufactured alternator (looked shiny and bright on the outside) which we just out of interest took apart before installing. The slipring was more worn than on the one we were going to replace.

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E39 530dA -02 M-Sport Messing metallic
E53 X5 3.0dA -06 Sport Stratus grey
E70 X5 40d -12 M-Sport Space grey