Review on Rectangular Grade Certificate 303 5308C by SHARS by Mike Wallace

I read about Joe Blocks in Simon Winchester's recent book The Perfectionists. He writes about it in the prologue. I just had to have her. I think I bought them mainly because 15-20 years ago a set wasn't as good as this one, would have cost a few thousand dollars, maybe more. Today they cost less than $100, all because of things in Winchester's book. What is confusing, however, is that I can't think of any other use for them other than ensuring the accuracy of my digital calipers. I'm not a locksmith and I don't have any tools (other than my digital calipers) that require this level of calibration. But they are so wonderful and perfect that I can't help but pick them up and look at them. If you know other useful uses for them, I'd love to hear about them.