Sorry to kick an old thread but as The Dude said new information has come to light...
Here's the 1988 Mets/Yankees Double Headers, save for the Mattingly. Check out the wrappers.
https://tinyurl.com/t3votfr
Guessing an advanced Mattingly collector picked up the set for the Mattingly and doesn't have a need for the others. Can't wait for these to arrive!