The 1979 book Wasn't the Future Wonderful? features the above two-page spread of Jack Dempsey challenging a robot. Unfortunately, the book doesn't specify the publication or date except that it's from the 1930s and probably from Modern Mechanix. Below is an excerpt from the piece.
I can whip any mechanical robot that ever has or ever will be made.
Maybe that sounds a bit egotistical, maybe you will say it's just the voice of a "has-been," but I assure you that neither is true.
Engineers can build a robot that will possess everything except brains. And without brains no man can ever attain championship class in the boxing game.
Gigantic Robots to Fight Our Battles (Fresno Bee, 1934)
Robots: The World of the Future (1979)
The Mechanical Man of the Future (1928)
The Robot is a Terrible Creature (1922)
Mammy vs Robot (Charleston Gazette, 1937)
Donald Duck's "Modern Inventions" (1937)
All's Fair at the Fair (1938)