Green’s Dictionary of Slang

(US) a dime, ten cents.

1926		D. Hammett ‘Assistant Murderer’ in Nightmare Town (2001) 142: Crossing each other, neither of us can make a thin dimmer.
1935		J. Conroy World to Win 57: I mooched the stem, and Dude there battered the privates. Most he got was a dimmer in cash.