I love Starrett tools, but
I've got a couple old Stanley squares. I've made them accurate by using a punch and a hammer. A couple blows near the inside of the corner narrows the legs, a couple blows near the outside of the corner widens the legs.
I recently dropped one so I had to set it up again. A pencil, punch, mallet and piece of paper - along with the square. 15 minutes later, it was dead on again.
I may buy a Starrett square some day. I've got several of their tools, but if it isn't guaranteed to be within a few thousands of square, why bother?
One thing I have learned is to never lend out a Starrett. I leant my neighbor my 12" combo square once. I have no idea how he bent it (only slightly), but he managed somehow. I like him so didn't say anything. He's a really good guy tho, because now I have 2 combo squares. :D
From now on the only person other than me that can use any of my Starretts is my wife the engineer.