The Further Adventures of Jimmie Dale

Jimmie Dale is a fictional character created by Frank L. Packard. He was a wealthy playboy by day, but at night put on a costume and became The Gray Seal, who enters businesses or homes and cracks safes, always leaving a diamond shaped, gray paper "seal" behind to mark his conquest, but never taking anything. He was just doing it for "the sheer deviltry of it" at first, but when a woman catches him she blackmails him to war on certain crime organizations. Jimmie Dale/The Gray Seal is often credited with popularizing and evolving what would greatly influence later pulp and comic book heroes. He also established the concept of a hero's secret hideout or lair, The Sanctuary, a precursor of the Batcave or the Fortress of Solitude.