Size they are using for washers is very similar to coin shape
It could be fun to do this on an actual coin.
One downside of this strategy can be for people with bad eyesight, but it's easy to use glasses or magnifying glass.
As a kid, I used to have a magnifying glass. Nowadays I get my phone to zoom in for the smallest things. How many people are going to make that mistake? I prefer to keep my fonts large enough to read.