my mate was telling me the other day that there was a certain batch of fucked up 20p pieces that were worth hundreds of pounds to dull, mo-money-than-sense motherfuckers. On the tail side, the vast majority of 20ps have a date. If you don't have a date on yours then you may well have a valuable one.
there you go, be sure to check every 20p piece that ever comes into your possession. And all i ask for is a meagre 15% finder's fee. No really, you're welcome