In looking through my red and black backs, it is clear that the red backs have more vibrant colors on the front. I looked at one card, the #57 Lopat card, and the cap and bill of the cap on the RB is colored all one color, while the BB version has some "shading" evident on both the bill and cap itself. In looking through the BB examples listed on ebay, most have the identical shading as mine, while two of the PSA graded BB versions have different amounts of shading on the cap than the others. The first scan is my RB, 2nd is the BB with the "shading" on the cap.
Here are two BB copies with the different shading on the caps than the other BB #57 cards listed on ebay:
http://www.ebay.com/itm/1952-Topps-E...item51b1eb176a
http://www.ebay.com/itm/1952-TOPPS-B...item2581945ae1
Could either of these two ebay listings be the "grey faced" variations?