Double denomination coins, like the $216 Washington quarter, are termed "planchet" mistakes.
The error happens during minting a blank coin (a "planchet").
If you keep your spare change in a jar, bowl, or piggy bank, you may want to check for valuable coins.
If you don't save extra change, look beneath sofa cushions, under your vehicle, and other places.
First, seek for coins with unique designs, "off" printing, or the incorrect denomination. Double-check.