Detective Comics #465 (1976)

THE BEST-KEPT SECRET IN GOTHAM CITY! During Batman's early years, he provided Commissioner Gordon with a fake identity in case the criminals try to learn Batman's secret from him. Eventually, Commissioner Gordon is kidnapped by hoods who want him to divulge Batman's secret identity, and he gives them the fake identity. When the hoods start looking for some Mr. Merrick, Batman is warned about Gordon's kidnapping. The Dark Knight goes to the place where Gordon is being held, and confronts with his captors.  After saving Gordon from peril, they decide to keep the whole affair a secret and they know that they'll have to come with a different fake identity, just in case. However, Commissioner Gordon is left to wonder about Batman's real identity and he thinks that perhaps he might have deduced it after all the years. THE ELONGATED PLAGUE!