Thanks for all of the great posts so far!
To Mike (post 7) --- good luck with the sale of your BL 460! You didn't post a link, so I will:
http://www.net54baseball.com/showthread.php?t=244708
I was looking for the overall 4 toughest non-scrap backs. I drew the line at 4 because overall Red Hindu doesn't match the top 4 --- some Red Hindu combos are really tough, but if all you want is any Red Hindu they don't rank with these 4. I don't know enough about the Cobb back to have a defensible opinion there, but I also wanted to see some cards get posted!
Brown Lenox were factory cut and will receive numerical grades unless they were altered. 100% of the Brown Old Mills are printer's scrap and will always receive an Authentic grade.
Here are two good articles about T206 back scarcity that owe much to a few of our esteemed board members:
https://www.psacard.com/Articles/Art...ifferent-backs
https://www.psacard.com/Articles/Art...ack-variations
Keep the scans comin!