I believe they use to be the checklist for the sets (Topps)
No team card in 1952 (http://portasite.com/?cat=180)
No team card in 1953 (http://portasite.com/?cat=181)
None in 1954 (http://portasite.com/?cat=182)
Don't see any in 1955 (http://portasite.com/?cat=183)
1956 is the earlist i could find.
The 1956 Topps Baseball card set is considered by many to be one of the most attractive and highly desired sets ever produced. With rival Bowman out of the way, Topps increased the number of players in their set and the number of cards produced. The most notable player omission was Stan Musial, who would not appear in a Topps set until his 1958 All-Star card. On the other hand, Mickey Mantle was the most heralded addition with his first Topps card since 1953.This was the first year that checklists and team cards appeared in a set.The key cards in the set are #135 Mickey Mantle, #5 Ted Williams, #33 Roberto Clemente, #79 Sandy Koufax, #31 Hank Aaron, #130 Willie Mays, #251 New York Yankees team card, #166 Brooklyn Dodgers team card, and both checklists. There are also 13 rookie cards in the set highlighted by #292 Luis Aparicio but missing from the set is the National League Rookie of The Year Frank Robinson. Card #8 of Walter Alston, #1 of William Harridge, and #2 of Warren Giles get a rookie card designation since it is their first appearance on a card.Cards 1 thru 180 have either white or gray backs with the first 100 cards containing more white backs while the last 80 cards contain more gray back examples. The remaining 160 cards in the set are all of the gray back variety.
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