The Diner's Club origin story is a myth. Unsecured credit lending actually originated with retail department stores.
Louis Hyman covers this story in Debtor Nation: The History of America in Red Ink (Princeton UP, 2011).
https://www.worldcat.org/title/debtor-nation-the-history-of-...
New Books in Economics podcast interview (Duration: 50:26):
Published: Fri, 04 Mar 2011 22:58:43 -0000 Media: https://traffic.megaphone.fm/LIT7526154990.mp3