Mantle '56
 

Can someone explain the gray back mantle '56. What are the other variations? When I look I can't tell. Which are rarer or more expensive? thanks

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1956 Topps
 

Cards 1 to 180 in this set can be found with white or grey backs, including the Manlte card which is # 135. Not sure there would be a premium difference on that card due to the back color. Others may disagree. It is my undestanding that cards 1 to 100 may be a little scarcer in grey, but that the oppostite may be true on 101 to 180. I think on the Mantle, the condition of the card itself would be the main gage of the value