I'm pretty sure that's Buck Barker's handwriting on the back of the Phelps. Barker wrote on the backs of his cards all the time. Here is a note he wrote on the back of an Exhibit card that I own (posted in this thread:
http://www.net54baseball.com/showthread.php?t=223647):
Here's a T212-3 with Barker's handwriting that Scott Gross posted (on this thread:
http://www.net54baseball.com/showthread.php?t=249451):
Other Barker cards have been posted on here before, but I don't have time to track them down right now.