This guy sells name brand squares that are blemished for a real good price (about $20) with free shipping. Cant really beat it and I figured maybe you guys would like to know. He also sells a lot of other tools.
I bought a 12 inch square with attachments that is perfectly square and looks great. I cant even find what is wrong with it.
For the same price, I found an old Rabone combination square, similar to the one that Paul Sellers is using, except that it hasn’t got the bevel pipe (or whatever that thingy is called). It took a while to find it, but I would wait again… it is perfectly square, robust, and I like the weight of the thick steel ruler.
However, I agree, it is good to know, where to find a good square. For example: DIY markets in Germany offer combination squares for 20 Euro, that are completely useless, a foldable yard stick does a better job. I had one of those cheap squares and it drove me mad until I checked it for squareness. It is way out of square, and I found, that even the ruler edges aren’t straight.