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When and why, in the DC universe, did Batman change the logo on his costume from just a black bat to a black bat set inside a yellow ellipse?
I ask because I remember the following story (see attachment) which shows Batman apparently too busy to go out with Robin. In the cover, there is a clue given "The tell tale clue is on this cover". In fact, the masked figure is not Batman but a criminal that has escaped but made the mistake that Batman had changed the logo from a black bat to one set inside a yellow ellipse.
I wonder if any reason was given for the change either in this story or one preceding this story. According to ComicVine "Robin, for his part, was able to instantly see through the "Batman's" deception due to the fact that the criminal's costume was out of date, and thus did not reflect the alterations Batman had made to his uniform, in the five years the other man had been incarcerated."