Gray backs exist for the entire set and white backs exist for cards 1-3 and 5-73 only (i.e., series 1 and 2).

My 1992 edition of "The Sport Americana Baseball Card Price Guide" by Dr. James Beckett prices this set as if there are 7 series, 36 in each except for Series 7 which has 24. However, the variation on card #4 (Jerry Priddy) is consistent with Series 3, not Series 1. So, I am labeling (in my own personal checklist, not here) the series as follows:
Series 1: (1 - 3, 5 - 37)
Series 2: (38 - 73)
Series 3: (4, 74 - 108)
Series 4: (109 - 144)
Series 5: (145 - 180)
Series 6: (181 - 216)
Series 7: (217 - 240)
This way, all the gray back / white back variations are in Series 1 and 2, all the Name on Front variations are in Series 3, and all the Printed Name on Back variations are in Series 4.
Feedback?

Probably the worst-looking designs from the 1948-1955 bowman collection. Although color was added, the backgrounds were also removed.