Does any country have measuring tick marks (inch/centimeter) on their currency?
I think about this every time I use a dollar bill to (roughly) measure something. A dollar is just a tad over six inches in length, so it sorta works.
I always think there should be real marks (inch on one side, centimeter on the other) along the back edge of all bills (or a least one dollar bills) 'cause they're a standard thing we all probably have in our pocket at any given moment.