Germans have long felt a nostalgia for their old currency. If you wander through the Christmas markets that thrive at this time of year, you come across stands which still take the Deutschmark.
You can buy your bratwurst with Germany's old money, which is accepted with a smile and then taken to the bank and exchanged for the true currency of Germany, the euro.
But now that soft yearning for the old is hardening - and a lack of affection for the new is also hardening.
Attitudes to the euro have been shaken to the core by the bail-outs of Greece and Ireland.
Suddenly, the unthinkable is being thought - and increasingly spoken. Where once the euro seemed as immovable as the Brandenburg Gate, now its future is debated by an increasing circle of people at the centre of German life.
Before the bail-outs, the periphery of politics discussed the demise of the euro as the common currency of 16 states. Now it's debated by men in suits who get driven around in large black cars.
People like Hans-Olaf Henkel. He's on the board of a string of big German companies and was president of the Federation of German Industries for five years.
He told the BBC that the euro was in danger of becoming a "transfer union" whereby money was transferred from northern European countries, particularly Germany, to southern European countries, particularly Greece and perhaps Portugal.
So, he thinks, split the two apart: let the strong economies in the north of Europe have their own euro and cut loose the weaker ones of southern Europe. France would be in the southern eurozone.
"It is probably the only way of avoiding huge debts piled up by the European taxpayers. The northern countries are usually countries that don't like inflation. They have a much tougher budget discipline. Whereas in the south, they are used to higher inflation and lesser budget discipline."
If it is not done, he thinks, money will continue to pour from north to south in an attempt to keep the current eurozone together: "I think it's not good for Europe that these two totally different economic systems are kept together by force, at the expense of taxpayers and their children."
Chancellor Angela Merkel has asserted that the situation is serious - but that it is important for the euro to survive. She wants a more robust mechanism put in place to cope with potential defaults.
But she cannot control the situation completely, and a vigorous anti-euro movement is gaining strength.
Juergen Elsaesser organises meetings, sometimes in the dank halls of old factories, and hundreds listen to his pro-Deutschmark/anti-euro message: "The euro is a bottomless pit which cannot be stabilised by Germans pouring money into it."
The difficulty for pro-euro figures, including the German chancellor, is a feeling among voters that the promises made by politicians when the euro replaced the Deutschmark have been broken.
Daniela Schwarzer of the Foundation for Economics and Politics in Berlin said: "Over the years in Germany, one important player dominated the discourse on economic policy and that was the Bundesbank, the German central bank. This was the institution which guaranteed German economic success after the Second World War and which was one of the reasons why Germany could regain some pride."
When Germany gave up its currency, she says, the political explanation to the public was that the euro would be just as stable.
Which is not the way it seems now to have been - hence the difficulty, and a difficulty detected at the immensely popular Bild newspaper, which often has a sensitive finger on the German pulse. It detects a shift of mood among the public.
Political editor Nikolaus Blome told the BBC: "I think there is still overall agreement to the euro in Germany, but underneath that loyalty and support for the euro there is a growing feeling of unease - unease with the fact that Germany may be about to bail-out other countries than Ireland and Greece - Portugal maybe, Spain, even."
Bild is very pro-euro and it has just started arguing against nostalgia for the old currency.
Mr Blome notes that it might be plain impossible to bail out some of the countries which may yet be in trouble - the sums would be too high. But he concedes that if more eurozone countries fail, and the bail-outs mount, then the clamour for an end to the euro in its current form may be unstoppable.
That would have political consequences. Rightly or wrongly, the euro was conceived as part of a wider project to unify Europe, all with the backdrop of World War II and the perception that Germany needed to be "bound in" to Europe.
Would a Germany free of the broad euro be as bound into that structure? Nobody knows.