Civil Guard has issued a warning on Twitter that coins from Uruguay are in circulation in Spain. They are very similar 2-Euro coins, but completely useless.
The 10-Pesos Coins from Uruguay reminiscent both in appearance and size of the 2-euro coins. The nominal value of 10 pesos from Uruguay are just 0.32 Euro – In Uruguay. Here in Europe they have no value at all.
The police are finding new 10 pesos coins all the time, so there may be reason to look more closely next you get the change back.