AACHEN, Germany - At the Café Koffeneck in the Dutch border town of Vaals, the imminent arrival of the euro is causing considerable apprehension behind the bar.
"We should put a sign outside saying: 'Only graduates in maths can drink here from January 1,' " said Marie-Jose Zenden, its owner. "We are used to mental arithmetic around this area, but next month is going to be something else."
Money has always been a tortured theme in this central pocket of the European Union, where the local language can change over the space of 30 metres.
Vaals lies a couple of miles from the German city of Aachen; the Belgian border is even closer. For decades, the German, Belgian and Dutch neighbours have muddled along, making up the rules of economic life as they went.
On a busy night, Ms. Zenden's takings arrive in the form of Belgian francs, German marks and Dutch guilders. Exchange rates are routinely totted up in the heads of local shopkeepers and businessman. But the euro may prove to be a maths test too far.
From next month, the world's most crowded currency zone will be obliged to use Europe's new money in addition to the other three currencies. All domestic currencies will be phased out by the end of February, although the Netherlands is making the change at the end of January. Until then, three nationalities speaking four languages will do their business using four currencies.
Ms. Zenden is wondering whether to bend the rules for the sake of her mental health. "The transition period will be hell on Earth around here.
"The Dutch government has told us that until January 28 we should only give out change in euros, while accepting francs, marks and guilders," she said. "That would mean that every night I would have to use three separate exchange rates that were entirely new to me. Can you imagine the queues at the bar?"
Instead, the Café Koffeneck's clients may experience a "Big Bang" transition to the new currency. "Up until January 28," said Miss Zenden, "everything could carry on as normal. But from then on, it will be euros and nothing else. And the customers will have to adapt."
Indeed, life for Aachen shopkeepers can only improve once the single currency is introduced.
Two miles down the road and an international telephone call away, Dr. Wilhelm Thevis, a chemist in Aachen, is about to call his bank for advice. "I still don't know what the rules are about accepting Dutch and Belgian money after January 1," he said.
Since 1989, Dr. Thevis has kept Dutch guilders and Belgian francs separate from German marks. Now, he has also bought a dedicated cash till for euros, along with a special calculator, which automatically converts marks into euros. But he has no technology to help him with Belgian and Dutch customers.
Franck Malis, the euro-transition expert at Aachen's chamber of commerce, is worried about parking meters. Until now, a parking meter in Aachen, Vaals, or the Belgian town of Eupen, has been a thing of wonder. Most accept anything up to six different coins from the three co-existing currencies. Now they must accept the euro.
According to Mr. Malis, that could cause problems. "There is a possibility that Belgian, German and Dutch euro coins may be subtly different as a result of separate production methods," he said. "We'll find out in January."