BERLIN — For the infrequent flier landing here from anyplace else in the euro zone, or at least for people with longish memories, there is still a lingering sense of novelty in the single-currency bills that do not need changing for the cab ride into town, the euro coins that buy an S-Bahn ticket in Berlin as easily as a Métro ride in Paris.

　　A German five-mark note with Albrecht Dürer’s portrait of a young Venetian woman. Today’s euro notes carry architectural motifs.

　　And, equally, there is a sense that those old Deutsche mark notes that preceded the euro — blue for 100s, green for 20s — did a pretty good job, too, even if you did have to buy them at banks or exchange booths, grumbling about inflated rates and usurious commissions.

　　It is, after all, only a brief nine years since Europe embarked on its greatest monetary experiment, trading national cash for a currency that optimists hoped would surpass the dollar. But as the euro has lurched in recent months from crisis to crisis over the indebtedness of some of the countries that use it, an older and unrealistic hankering for its predecessor is emerging.

　　Two years ago, opinion surveys here placed the number of Germans pining for a return to the mark at around a third. Now the figure is around half. At his open-air emporium of traditional seasonal fare, Joseph Nieke even accepts the old notes, which may still be exchanged for euros. “Bring out your marks!” says a sign next to the steaming kettles of mulled wine and trays of mettwurst and other pork products at a Christmas market on Unter den Linden near the State Opera.

　　He might get a shock if the entire nation took up his offer: according to the central bank, there are currently some 13.45 billion marks, the equivalent of roughly $8.7 billion, still to be handed in, squirreled away presumably under mattresses or in drawers, wallets or safety deposit boxes. That’s about 110 marks, or $70, for every one of Germany’s 80 million people.

　　Currencies, of course, are not just about money and, far more than in many lands, a chunk of recent German history has been inscribed on its bank notes.

　　In 1948, currency reform replaced the reichsmark, or imperial mark, with new marks, not once, but twice over — one for the Allied-occupied West and one for the Soviet-dominated East.

　　As the two Germanies grew ever more estranged, their bank notes mirrored their distinctions, reflecting what was called the abgrenzungspolitik, whereby East Germans laid claim to all that was good in Germany’s tortured history and ascribed the bad to the capitalist West.

　　Though technically worthless in the West as the inconvertible currency of a state-controlled economy, so-called Ost-marks proudly bore the portraits of Goethe and Schiller along with those of Marx and Engels. (In the 1960s, early Western bills displayed images reflecting values like civic pride and openness to the world.)

　　Across Europe, indeed, bank notes offered microcosms of national self-image. Symbols of inventiveness and élan, French banknotes portrayed the Curies, even though Marie Curie was Polish by birth, and the aviator Antoine de St. Exupéry. (In France, by law, most receipts still offer a conversion from euros to French francs, so nostalgia may not be an exclusively German characteristic.) Printed in fine shadings of blue, green and brown, Portuguese escudo bills celebrated the navigators who plied the oceans in their wooden ships, making landfall in Africa, India and the Americas.

　　After the fall of the Berlin Wall in 1989, East Germans confronted a new shift when their currency was replaced by the Deutsche mark as part of the reunification of Germany. Just over a decade later, the euro was introduced, first in electronic trading, then, on Jan. 1, 2002, in the cash economy of an initial 12 European countries. That number has now grown to 16 countries, and is soon to be 17. All of them claimed to have signed up to standards of fiscal discipline, but some of those pledges now seem illusory.

　　In symbolic terms, the new euro bills with their bland, architectural neutrality almost seemed to represent the end of national pride and history: gone were the great navigators, poets, playwrights, inventors, ideologues. In came — bridges.

　　But in many southern European countries, the new currency offered a rite of passage into a club of northern prosperity and stability.

　　“The euro opens the geographic door,” said the Rev. Manuel Horacio Gomes, a Portuguese priest who was part of a broad campaign by the Roman Catholic Church to spell out to congregants the pros and cons of the euro.

　　The perils of that particular portal took less than a decade to emerge in the debt crises savaging the euro zone this year, with bailouts in Greece and Ireland, and nervous governments in Lisbon, Madrid and elsewhere pondering how far the contagion will spread as speculators seek to exploit the currency’s frailties.

　　It is happening at a time when many Europeans see Germans as uncoupling their own interests from the continent’s, reluctant to pay a cent (or pfennig?) more to rescue the profligate economies of their southern partners unless they finally sign on to Germany’s own standards of hard work and thrift.

　　And it is happening as the European debate takes an ominous turn. If it is argued that for the euro to work like the dollar works, it will have to be backed by the same political and fiscal cohesiveness as found in the United States, then the converse also holds true: as the currency goes, so goes the Continent.

　　“With every day that passes, the crisis of the euro is becoming more and more a crisis of the European Union,” wrote a columnist, Matthias Nass, in the weekly Die Zeit.

　　For all their nostalgia, most Germans are realists. Many might yearn privately for the old bills and the sense of ironclad, anti-inflationary security that came with them. But, like the political and business elite, far fewer believe that the clock may be reversed without severe economic hazard. And, with growing resentment, many here acknowledge that weaker economies will look to Germany to perform yet one more miracle, after postwar revival and the huge costs of reunification.

　　“The truth is,” Mr. Nass wrote,