Allen & Ginter SP question

Just bought a hobby box of A & G, picked up a Granderson auto and a Markakis auto, a mini Mantle and two mini black with no number, among other nice cards. But, how do we know what cards are SP's? And has it been determined that the black minis with no numbers are errors? By the way, at the National show A & G 2007 are going for $99 a hobby box....John
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