Thanks Hank. PM6 isn't covered in Paul Muchinsky's book. I also have a copy of "Non-Paper Sports Collectibles" by Hake/Steckler. It's not there either.
When I saw the pin listed, I struggled to find any details about it. That's partly what got me interested. A Google image search brought me to the pre-war cards page.
There are 8 pins in the set. As you mentioned....no commons.
- Grover Alexander
- Ty Cobb
- Bucky Harris
- Rogers Hornsby
- Walter Johnson
- Babe Ruth
- George Sisler
- Tris Speaker
I could only find one other PM6 listing for sale
https://ebay.us/iV3Hqy
There are no sold listings and only 12 PM6 pins ever graded at PSA.
If anyone has any other info, I'm keen to learn more.