[rommesc]

Pat,

Thank you for compiling this information and sharing the research. Have been tracking these print defects as well. Agree with your theory about these subjects sharing the same position on the print plates used for Polar Bear cards. Besides the Mathewson/Meyers/Pelty that share the same back marking, I also have these two cards:
1) Tannehill(Follow through)
2) Cy Young