When I first looked at this Mitchell card I thought at some point it had
been marked with a black marker.
Mitchell.jpg
But after a little research it turns out the mark occurred during
the printing process.
Mitchell With Black Mark.jpg
SGC doesn't put MK qualifiers on the their cards but if this card was sent
to PSA for a crossover it would most likely receive a MK qualifier and
rightfully so. Even under magnification you can't tell that it occurred
during the printing process.