Not the earliest, but I have always thought that the batting glove on Bill White in '69 Topps created a focal point (not my card). Hawk Harrelson was said to be the first player to use a batting glove in '63 or '64 (actually a golf glove). No cards that I can find of him in the 60's showed him with his glove.
Edited because I just saw the post about the '57 Topps Robinson. I never noticed that.