For as long as I can remember I've been using a pair of cheap plastic calipers bought from a long ago fleamarket stall. I finally found a pair of quality digital ones at a price I can live with. They're far easier to use and much more accurate.
Available currently at your local Harbor Freight, $9.99.
Non illegitimis carborundum est. Excellent advice for all coins.
Make Numismatics Great Again!