The European Commission’s top economists warned the politicians in the 1990s that the euro might not survive a crisis, at least in its current form. There is no EU treasury or debt union to back it up. The one-size-fits-all regime of interest rates caters badly to the different needs of Club Med and the German bloc. As events now unfold with vertiginous speed, we may find that it destroys the European Union instead. We are fast approaching the moment when events decide whether Europe will bind together to save monetary union, or fracture into angry camps. Will the Teutons bail out Club Med? If not, check those serial numbers on your euro notes for the country of issue. It may start to matter.