Question about the 1956 Topps Sandy Koufax card......

I need to get this card for a friends Birthday. I collect Pre War and not really familiar with this issue. Let me know about the White and Grey back. I have read where the white is more desirable vice versa. I have absolutely no clue. Thanks in advance!
"If someone tells you that money is the root of all evil. They don't have any"
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Comments
Cards 101-180 command a 50% premium if they are white backs and they are very hard to find. Cards 181+ are all gray backs.
Here is a pic of a very nice Koufax if your interested. They are hard to find centered like this.
Jeff