> found it in my "piggy bank", thought it was a US quarter at first. Looks like it has
> "CARL GUSTAF" on the front?
It's a Swedish 1 krona coin (aka "1 crown"). The exchange rate of SEK into USD is about 11 cents per dollar.
The Swedish krona used to be subdivided into hundredths, called öre, but commensurate with the rise in electronic payment, use of the öre was scaled back to just the 50-öre piece in 1991, with the öre no longer being minted entirely in 2009, and no longer being legal tender in 2010.
So, yeah. Here in Sweden, the smallest amount of currency available is equivalent to about a dime. The other denominations of coinage are 5 SEK, 10 SEK, and the recently-reintroduced (after being phased out for a while) 2 SEK coin. Beyond that, bank notes are available in denominations of 20, 50, 100, 200 (which was only introduced in the past few years), 500, and 1000, though you'll rarely see 1000 SEK notes outside of casinos.
The bank notes themselves are each a unique color as well as a unique size, increasing alternately in width and height as they increase in denomination, so that they can be more easily differentiated by people who have impaired vision.
Amusingly, my partner has a 2L jug absolutely full of 10-öre coins. They're completely worthless now of course, but it's a cool conversation piece.