I built a computer vision device that used the top-down area of a penny as a calibration standard. Coins are useful, easy-to-get items that have relatively tight manufacturing tolerances.
Have you?
We use a pack of cigarettes as a gauge for one of the jobs we do. Quick, (not so) cheap, and readily available. May have to standardize on a vape though in the near future.
Of course there's a limit to the precision you can get from coins, but considering the scale of their production and the account of handling they see they are surprisingly good
It's been happening since ever.