I did a quick little google research. Apparently the regular black ones are serial #d /60 (on back) and the Wal-Mart Black are not serial numbered.
Plus: The Wal-Marts have the background tinted black so it looks like the player is in a "black" void and the regular black are just the black borders with picture background untouched.
http://www.comc.com/Cards/Baseball/2011/Topps_Black
http://www.comc.com/Cards/Baseball/2011/Topps_Wal-Mart_All-Black
I collect: Baseball, Football, Hockey, Mostly Vintage pre1980, My Homie teams - Washington/Baltimore Teams Senators (Twins, Rangers), Expos/Nationals, Redskins, Capitals, Bullets/Wizards - HOFers - Non-sport (mostly TV shows and movies).
My Trade List is very much a work in progress
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