I put my money on Mitutoyo. The scale is made in Japan the rest Mexico.

PEC USA are nice but not the same quality IMHO. But very close and would be my next choice for a good square.
Starrett has several different lines and the cheaper ones aren't very nice. You have to spend big money to get something comparable to Mitutoyo.
But for the money PEC USA is a steel at
http://store.harryepstein.com/c/Squares.html pick up the 18 and 24 scales they are uselessly $75 each.
Thanks for the link Rodm,
Those are great prices on PEC squares but they are blemishes which isn't a big deal but I don't think they the hardened version but they sell a 12" PEC combo square for $20, that's pretty much free so there's no reason to complain.
I'm wondering if there is now different levels of quality being issued by the same companies without noting the difference. My PEC looks slightly thicker and more stout than what i'm seeing in the pics.
Man looking at the new level of global manufacturing and economics makes it really tough to figure out what your really getting, not a good thing in the world of reference tools. The world of squares and accurate reference tools is getting very squirrelly.
Your right about the Mitutoyo heads being made in Mexico, I do know that Mitutoyo has a good chunk of there blades made in the USA by PEC.
On the Grainger site it lists Mitutoyo made in Brazil but you can see in the photo that it's printed Mexico on the head.
If you can find an all Japanese Mitutoyo then your in good shape but I would definitely hesitate on the mexican version without it having over ten years of positive feedback. I certainly would not buy a PEC square made in India, it's not worth it.
There's absolutely no point of buying a reference tool without it having a good long track record. This new global sourcing of reference parts from different factories pretty much reduces the reliability and lowers the chances of getting something equal to old school Starrett USA quality. Maybe keep an eye out for a Brown & Sharpe, it's hard to beat the old school of reference tools but I'm not quite so sure about these new world versions.
Sorry for the rant