Brian Micklethwait asks a pertinent and subversive question.

If we know which Euro currency notes are issued by which country, why not start insisting to be paid only in notes issued by countries which are unlikely to default?

… supposing lots of people do know this, or get to know it, does it not provide a mechanism by means of which mere people might hasten the collapse of the more dubious EUrozone economies, by demanding, when being paid in actual money, to be paid only in Euros printed by the undubious countries?

Perhaps the answer might go: but making such judgments would be, in EUrope, illegal. Maybe so, but that won’t stop a black market making minute comparisons between differently lettered Euros, nor will it stop tourists in other parts of the world, planning their EUropean trips, demanding, once they hear such stories, to receive only the kinds of Euros that they would like.

They could, for instance, refuse to accept the wrong kind of Euros, or, if given a mixture of good Euros and bad Euros, sort out the good from the bad and swap the bad ones back for pounds, or dollars, or whatever.

The wrong kinds of Euro notes, from the dubious countries, could soon be treated exactly as if they were forgeries, could they not? The big difference being that these forgeries will be easier to spot…

Wikipedia tells us that we can indeed ascertain which country has issued which notes:

Unlike euro coins, euro notes do not have a national side indicating which country issued them (which is not necessarily where they were printed). This information is instead encoded within the first character of each note’s serial number.

The first character of the serial number is a letter which uniquely identifies the country that issues the note.

Thus X denotes Germany, U France and so on. Greece as it happens is Y.

Scope for mischief-making here?

Not much, according to numerous sagacious commenters including Tim Worstall:

… the cash euro is such a tiny part of the money supply across the EU zone. Electronic euros are vastly more important and there is no differentiation between them.

So there.