User blog comment:Battymanis1awesomeguy/batman comic/@comment-1038387-20150914025823

Check the first couple of story pages for a story title and/or writer and artist credits, and the index (the white box at the bottom of the first story page). That should give us some idea on which time it was published. Because he's been around for 75 years, and the Joker's Ace Chemicals origin shows up every so often.