In it's last published Standard Catalog SCD recognized the 52 Mantle and Thompson and Robinson as variations due to the fact they were double printed and had front and back differences. On all three the most basic differences are that the stiches on the baseballs on the back run either right or left. But all 3 have front differences as well. On the Mantle the easiest front differences for me are either the truncated or not truncated e in the auto and the straight or wavy stars on the top of the box
