Fearless, getting a little warmer here. Apparantly Mr. Benzon lost his money principally in horseracing. He was the "Man of the Day" in Vanity Fair Magazine, July 23, 1887 [on which a bricks-qand-mortar library may help]. See also the site wwh noted above, listing his nickname as The Jubilee Plunger.

In some dictionaries is plunger is listed as having the meaning gambler.

http://www.race-horses.com/news/2000/aug2000.htm; near bottom
http://www.defreitasbooks.com/20vanity.html