My unknown hobby

I like collecting rare coins. The other day, I saw a very rare 5 yen coin in the cash register when I was paying at the cash register at a convenience store. I've been collecting the rare coins since I was a child, for about 25 years. But I encountered and got only 6 coins in the meantime. They are very rare coins. There are my own rules for collecting rare coins.

- Don't ask a cashier to exchange coins.
- Don't get rare coins at old coin shops.

So, that is why I couldn't ask the cashier to exchange it. The rare 5 yen coins were made from 1949 to 1958. The difference between normal one and rare one is the font type. The rare one has calligraphic fonts and normal one has Gothic fonts. It seems you can hardly tell the difference, but you can tell easier with matte brass color at first sight.