Definitely not part of the X3.
However it looks very much like the lower grill section on front of a '97 - '00 E39 5 Series. The two holes on the top can be released to remove the fog light for lamp replacement.
I'm sure it just dropped in the box as they were packaging up your part.
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'13 X3 28i M Sport Carbon Black Metallic w/Oyster Nevada
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