From the "Collecting Snap-On" website
"Milwaukee Tool & Forge Company (MTF) made open-end wrenches, punches and chisels, sockets, toolboxes and other related tools in the 1920. Recently early Sockets with the Snap on marks and the nearly identical sockets with the MTF marks have been found creating speculation that MTF may have been an OEM source for socket blanks in the 1920s."
You may have discovered another part of the puzzle....
Chilly