Joker First Appearance: Batman #1 and How to Identify It

Joker first appeared in Batman #1 (cover date Spring 1940), published by DC, by Bill Finger, Bob Kane, Jerry Robinson. The source puts it this way: "This book features the first appearance of The Joker and The Cat (Catwoman).".

• Cover date / release date: the issue's release date is recorded as March 6, 1940.
• Interior character introduction: the story introduces the Joker as a psychopathic criminal mastermind with a warped, sadistic sense of humor.
• Visual inspiration for the character design: the Joker's look was inspired by the 1928 film The Man Who Laughs, which featured a grotesque character named Gwynplaine, played by Conrad Veidt.

• Indicia: the small print on the first page or inside cover gives the issue number, date and publisher; reprints usually say so there.
• Cover price and barcode: a price or barcode format that did not exist in the year printed means a later edition.
• Paper and staples: decades-old newsprint is tan at the edges; bright white pages on an old date are a warning sign.
• Restoration: color touch, trimmed edges and married covers are common on expensive keys; a grading service can detect them.

Shoot the front cover flat, straight on, in even light, then the indicia page and the back cover. Include the top edge and staples in one frame. The app reads the title, issue number and cover and matches it against the checks above; the indicia photo settles most reprint questions.