A little bit of knowledge is not always a dangerous thing, as a friend of ours, in the Algarve for three months to 'test the water' before possibly making a permanent move here, recently found out.
Unfamiliar with those wonderful pieces of metal so prone to ripping holes in one's pockets, the centimos (and 1 and 2 Euro coins), she did not scrutinise too closely the change she was given for some small purchases made in one of a number of beachside shops and cafes she recently visited. It was only when she subsequently tried to spend the alien lucre that she was made aware that the strangely silver coins were nothing to do with the good old Euro and it's diminutive offspring.
Closer inspection of the dodgy doubloons revealed them to be from the Czech Republic - not really a member country of the Eurozone.
While the message here is cautionary - always check your change - the irony of this particular situation is that our friend, who for many years has lived in the UK, is by birth, Czechoslovakian.