Cash is now used very rarely and coins are used even less. But I found the 1921 dollar coin to be a really interesting coin.
This 1921 dollar coin may look ordinary on the outside, but it actually has a hidden thought inside. Pull out the sword on the face of the coin and insert it into the groove on the side of the coin. The window in the pattern will open, and vice versa. It can be seen that the craftsmen at that time put a lot of thought into the design, and it may also be a process to prevent imitation.
Such a fun coin is great to play with when you have nothing to do.