When I was growing up, Kellogg's had a "coins of the world" promotion in my people's land. They would have low denomination coins from all over the world, one or two per cereal box. The Japan coin was the 1 yen coin, sometimes the 5 yen coin. At the time, it was 350 yen to the dollar, so it wasn't exactly a major treasure find.

By the way, the coins were exactly the same, even the same cheap aluminum feel.

You could keep a bunch for passover and use them as afikoman.