Knuckle Sandwich Meaning

(slang) A punch to the face, especially to the mouth.

Example: 1957, Jerome Chodorov and Joseph Fields, Anniversary Waltz: Comedy in Three Acts, ISBN 9780822200505, p. 20:
  OKKIE. (Raises his fist, kissing the knuckles menacingly—follows her to bottom of steps.) How would you like a knuckle sandwich?
2002, Ira Berkow, "Sports of The Times: A Babe Ruth Myth Is Stirred Up Again," New York Times, 7 Apr. (retrieved 7 June 2009):
  Rather than an embrace, the Babe would most assuredly like to have given a knuckle sandwich to the executives of that candy corps. Or hit them over the head with his 42-ounce bat.