Here is what I believe. I put this together partly by my own research and partly with the the help of others in this thread http://www.thegaragegazette.com/index.php?topic=19053.msg243123#msg243123
at The Garage Gazette when I found this Craftsman wrench with a Snap-on date code.
The patents on my wrench go back to John W. Lang and are assigned to A&E Incorporated of Racine, Wisconsin. Racine and Kenosha are only a few miles apart and Daniel M. Lang, the founder, was an engineer at Snap-on who started the company to make feeler stock and other items to be sold to Snap-on. A&E acquired or started a couple other companies and brands including Kastar. Kastar makes the above wrench and OEM's it to others mostly private branded. For some reason Kastar uses the Snap-on date codes even on items not marked Snap-on. Perhaps it's just because of the close history the two companies have or maybe they just want the wrenches date coded and the codes are already worked out. Interestingly, one of the A&E companies, Eckmann Custom Products, does metal stampings like the sides of these laminated wrenches.
Here is a link to one catalog page from Lang Tools web site showing the twins to your wrenches:http://www.langtools.com/wratcheting-wrenches/flat-wrenches.html
So I am going to venture a guess and say your wrench was made by Kastar, private branded and like what seems to be most of the Kastar laminated ratcheting wrenches carries the Snap-on date code.