It's a conduit wrench. See add below from July 1948 Popular Science Magazine.
They actually made more sizes than stated in the ad. I have the following numbers:
3, 4, 6, 8, 10, 12, 20, 22, 24 and 28. I don't have a 7 or 14.
(http://i222.photobucket.com/albums/dd3/buswrench/message-board/JoarWrenchAd1948PopularSceince.jpg)