Here's my latest acquisition... a check from Casey Stengel to the Mets' ballboy (batboy?), dated September 23, 1962...
9/23/62 was the final home game of the season, and at the time it was thought to be the last game ever at the Polo Grounds, with the Mets expected to move into Flushing Meadows Stadium the following season.
Presumably the check was an end-of-season gratuity, and it's interesting to note that the "Ol' Perfesser" misspelled the young man's name, as seen by the endorsement signature on the back.