Might want to look into the Western Forge Date codes. They are almost correct. From what I gather the letters should correspond to a year. They used up all their single letters for date codes by last year (2010). Example 2010 ended with Z and the newer 2011 stuff I saw all started over with an AA code. So Z is 2010, Y is 2009, X is 2008, etc, etc. This has been my observation of screwdrivers and adjustable wrenches made by WF, but I can't say I'm exactly certain of it. Just something to look into.
Also there are manufacturers that I know make or made tools for Sears that are not listed there for newer stuff. Lisle, Klien, Midwest, and some others are all missing.
With regards to National Handtool, not sure about the Taiwan conection, they are Stanley owned, but are still operating in Texas making tools here in USA, much of the modern Proto hand tool production was shifted there by Stanley after they aqcuired the Proto and Blackhawk brands.