Adventures of Jimmie Dale

Published in the early 20th century, 'Adventures of Jimmie Dale' by Frank L. Packard follows the dual life of Jimmie Dale, a wealthy playboy who becomes the masked vigilante known as The Grey Seal. He engages in safe-cracking exploits, leaving behind a diamond-shaped grey paper seal as his calling card, initially for thrill but later compelled by blackmail to combat crime. This character is notable for influencing later pulp heroes and establishing tropes such as the secret lair and the playboy alter ego, impacting figures like Zorro and Batman.