Fritts and DaClyde, thanks for the information.
I found a Bucky Dent card possibly from the same set as the Rivers card as it has a black back and MLB logo, too. I couldn't locate anything close in design to either of these searching for TCMA or 1980s SSPC. I also searched for All-Star Magazine sales and found some on Ebay - none for Yankees with cards, but there were some for other teams and the backs don't match, plus they are in sheets with dashed lines for cutting.
I also located a blog where at the end of it he has a section entitled Fakes / Reprints, and he states: "Haven't seen any in the marketplace." Prior to that he says that the company secured licensing from both MLB and MLBPA.
HOWEVER, the backs to those cards from some Ebay vendors are blue and dashed.
Right now I'm going to leave the cards under the 270 set, but will see if I can find more information later.
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“Aslan didn't tell Pole what would happen. He only told her what to do. That fellow will be the death of us once he's up, I shouldn't wonder. But that doesn't let us off following the signs.” - Puddleglum in The Silver Chair by C. S. Lewis