Scored a Starrett combo square for $40 at a garage sale - too good to be true?

So I was hitting up some garage sales this morning and found a guy selling a bunch of old tools. Picked up a Starrett 12" combo square for $40! It's got some rust and the level vial is cracked, but the blade looks straight. Did I just get the deal of the century or is there something I'm missing? I know these things are like $150 new. Any tips on cleaning it up without ruining the markings? Also, how do I check if it's still square? I'm pretty handy but not a machinist lol.

First off, nice score! But before you get too excited, check the blade for wear. Starretts are great, but if it's been dropped or used as a pry bar, it might be out of square. To check: set it against a known straight edge (like a machined edge of your table saw) and scribe a line, then flip it and scribe again. If the lines match, you're good. If not, it's wall art. Also, that cracked vial is a safety issue if you're using it for leveling - replace it or don't rely on it. For rust, use evaporust or fine steel wool with oil, but go easy on the markings. They're etched, so too much scrubbing will erase them. Good luck!

Carl's advice is spot on. I restore old tools all the time, and Starrett squares are tanks. That rust is likely surface only. I'd start with a razor blade to scrape off the heavy stuff, then hit it with some 0000 steel wool and WD-40. For the vial, you can get replacements from Starrett or McMaster-Carr. But honestly, for $40, even if you have to put $20 into it, you're still way ahead. Just make sure the head isn't cracked or the locking screw isn't stripped. Those are the weak points. Post a pic if you can!

Man, I never find deals like that. Around here, people want $80 for a rusty no-name square. Congrats! I'd be curious to see how it cleans up. I've heard that a vinegar bath works too, but it can dull the finish. I'd stick with the steel wool method. Also, if the vial is cracked, you might be able to pop it out and replace it with a generic one from the hardware store if you don't want to pay Starrett prices. Just make sure it's the right size. Let us know how it turns out!

One more thing - after you clean it, check the 45 degree edge too. Sometimes those get dinged up. If it's nicked, you can file it flat carefully, but that's advanced. For most DIY stuff, as long as the 90 is good, you're golden. And yeah, pics or it didn't happen!