Checking Polish money is not counterfeit
Just found this on the Bank of Poland's website in English - good for visitors for Euro 2012 as gives some guidance on how to detect and avoid fake banknotes.
Some of the advice from the PDF:-
Check all security features to make sure
that the banknote is genuine
10 zloty and 20 zloty notes
¥ Feel the printed elements that can be identified by touch
¥ Look at the watermark and check its authenticity, look for
the security thread with micro lettering and the perfect matching
of elements complementing each other on the front and the
reverse side of the banknote.
An attempt to pay with a counterfeit banknote is a criminal offense.
Counterfeit banknotes are seized without compensation (Article 35 of the Act on National
Bank of Poland (Dziennik Ustaw 97.140.938 as amended), Regulation of the President of
the NBP on seizure of counterfeit notes and coins (Monitor Polski 89.32.255 as amended).