1956 POP REPORT Help "Please" Baseball

I've listed some cards on the BST board and was going to list some more when I noticed huge variances in the pop report on the Low numbers in regards to White and Gray Backs. The cards I was looking at were #'s 51, 57 & 73. They had low pops of like 12 in Gray and over 100 pop in white backs for these numbers. Mine are gray backs for the numbers listed. Does any of this mean anything or did PSA just not list the colors years ago?
Thanks in advance.
Mickey71
Thanks in advance.
Mickey71
0
Comments
PSA didnt start putting the back color on the flip until a year or so ago. The white backs do fetch a bit more, but not a true rarity.
I think it is 101-180 are the WB's the command the most. I could be wrong, but it something close to that.
I am sure others that are more familar with the 56's will chime in.
1957 Topps 99% 7.40 GPA
Hank Aaron Basic PSA 7-8(75%)
Jeff