This part was purchased at an Amazon return center. Looks like it was attempted to be installed but never put on vehicle.

BCB96659

This brake caliper and bracket set is a direct replacement for the rear passenger side of Mercedes-Benz models including the C250, C300, C350, E350, and E550 from 2010 to 2017. The set includes a metal piston and mounting bracket for easy installation. It is compatible with other part number 344431 and interchange part number 19-B6659. The manufacturer offers a 1-year warranty for this product. Please note that this product is subject to California Prop 65 Warning.