The signature reading 'A. Hitler, 1910' is inscribed on the watercolor "Nelkenstrauss" (carnation bouquet), which went on sale in June 2015. Watercolor paintings and drawings by Adolf Hitler are set to go up for auction again on Saturday. (Christof Stache/AFP/Getty Images)

Before he set out to build a Nazi empire and exterminate Europe’s Jews, Adolf Hitler toiled as an artist on the streets of Vienna, supporting himself by selling hand-painted postcards of city landmarks.

The fascist state that he sculpted no longer exists, and the German criminal code devised after the war sought to erase its traces by banning Nazi iconography, including swastikas. Giving the Hitler salute is punishable by up to three years in prison. Holocaust denial is also verboten.

But Hitler’s creative vision lives on, in the form of sketches and watercolor paintings that bear his name, though some are thought to be forgeries. By his own account in “Mein Kampf,” he created as many as three works a day during his stay in Vienna between 1908 and 1913.

More than 30 pieces signed “Adolf Hitler” or “A. Hitler” will go up for sale Saturday at an auction house in Nuremberg, in southern Germany — part of a trade in Hitler’s creations that some find reprehensible.

The sales are “repulsive and sick,” finds the British art critic Jonathan Jones. In a 2015 column, he asked, “Who are these collectors that fork out considerable sums for the art of a man who caused murder and cruelty beyond imagining?”

The only consolation, he reasoned, is that many of the pieces turn out to be fakes.

A catalogue prepared by Nuremberg’s Auktionshaus Weidler indicates that the “special auction” will include “pictures signed or monogrammed” by the dictator, spanning 1907 to 1936. The items come from private collections in Austria and elsewhere in Europe — from “famous artists of the Third Reich” or their heirs, as well as from the estates of collectors.

The highest starting price is 45,000 euros, or about $51,000, for a landscape of a lakeside village, rendered in light blue and deep green watercolors. The lowest ask is 130 euros, or close to $150, for a study of a small-town monastery. One of the pieces is a nude drawing of Hitler’s half-niece, Geli Raubal, who lived with him in Munich and is thought to have used his gun to kill herself in 1931.

Trade in Hitler’s art is allowed in Germany as long as prohibited symbols do not appear. Still, the transactions rarely escape controversy, particularly in Nuremberg, where the Nazis staged annual rallies and passed a set of laws stripping Jews of citizenship in 1935. After the war, the Bavarian city hosted the war crimes trials that gave rise to the declaration, “Never again.”

Bids for the pieces come from China and the United Arab Emirates, as well as from within Europe, the Nuremberg auction house has said. One of the auctioneers, Kerstin Weidler, defended the works as historical artifacts, denying that buyers were “all old Nazis.”

“Not at all,” she said in a 2016 interview with Germany’s public international broadcaster, Deutsche Welle. “Among the buyers, we have collectors who want to own a piece of world history. There are customers from all over the world, for example a museum in Brazil.”

Weidler said the auction house assesses the authenticity of the works using lighting tests and by comparing the images to a catalogue of Hitler’s material, developed in the 1930s using the main Nazi archive. The credibility of Nazi-era efforts to verify the works stands in question.

It is difficult not to read Hitler’s crimes back into his artwork, though its mundane and mimetic quality resists such interpretation. The prosaic pieces suggest that his ambitions were once starkly different from what he ultimately carried out, observed Deborah Rothschild, who curated a 2002 exhibit on Hitler’s early years at the Williams College Museum of Art in Massachusetts.

“I want to take him down a notch,” she said that summer in an interview about the exhibition. “He’s not an evil genius. He wasn’t born evil. If things had gone his way I think he would have been quite happy to be an academic art professor.”

The works up for auction in Nuremberg range in style but mostly reveal the aspiring artist’s dedication to craftsmanship and precision, and his tendency to imitate simple patterns from mass-market imagery. He particularly admired the Italian Renaissance and early baroque traditions, as well as genre painting.

Others say the art makes the viewer, and especially the collector, complicit in the acts of its maker.

“If looking at a painting can be said to constitute a moment of intimacy with its painter, then collecting art by the unhinged is tantamount to getting into bed with a madman,” a columnist in the Guardian wrote in 2009, after a Hitler trove was sold in Britain for the equivalent of more than $100,000. Those pieces, discovered after the war by a British soldier in Germany, had apparently sat in a collector’s garage ever since.

The Nazi leader isn’t the only abhorrent figure whose artistic inventions elicit curiosity, turning otherwise quotidian images into desired commodities. A clown self-portrait painted in oil by John Wayne Gacy, who assaulted and murdered at least 33 men and boys between 1972 and 1978, recently sold for $7,500 at an upmarket auction in Philadelphia. The prices can be much steeper on entire websites devoted to the trade in serial killer art, featuring works by Charles Manson and Richard Ramirez.

The Nuremberg auction house has established itself as a leading purveyor of Hitler’s work. In 2015, it reaped $450,000 for 14 pieces by the Nazi dictator.

Questions about authenticity have dogged attempts to distribute Hitler’s art. The upcoming auction will come two weeks after German authorities seized three watercolors, set for sale in Berlin, because they suspected that the attribution to Hitler was erroneous.

Other custodians of Hitler’s art have made different decisions about what to do with the material.

The policy of the Bavarian state archive is not to pay for the works but only to accept them as donations. Herbert Weidler, the head of the Nuremberg auction house, has similarly sought to avoid being seen as profiting unduly from the morally dubious artwork. But when he pledged to donate part of the proceeds to a historic preservation society in 2014, according to the Nürnberger Nachrichten newspaper, the group declined to take the money. The preservation nonprofit called the suggestion that it was unconcerned with the source of its funding a “great wonder.”

Four watercolors remain in the hands of the United States government, decades after they were seized by the American Army — and used as evidence at the Nuremberg trials. In 2003, a federal judge in Washington turned back efforts by a Houston-based collector of Nazi memorabilia to claim the works based on an agreement with heirs of Heinrich Hoffmann, Hitler’s friend and photographer.

The pieces are locked away at the U.S. Army Center of Military History in Washington, available only to scholars.

Those who want to understand Hitler and the devastation he wrought would be wise to examine the works, advises art historian Birgit Schwarz. More attention has been paid to the despot’s tastes as a collector, to the artistic plunder he oversaw during the Third Reich and to his crusade against modern masterpieces that the Nazis labeled “degenerate art.” Whole exhibitions have been devoted to the denigrated material.

But in Hitler’s own paintings lie clues about his self-conception as a creative mastermind, Schwarz said in a 2009 interview with the German magazine Der Spiegel.

“Hitler’s deluded view of himself as a genius is based on the confused system of thought emerging in the late 19th century, which centered on the idea that a genius — a strong personality who outshone everything else — could do anything and could do anything he pleased,” she said. “His love of art led directly into the heart of evil.”

Twice rejected by the Austrian capital’s Academy of Fine Arts, Hitler continued to see himself as an artistic genius.

As German troops marched on Poland in 1939, the Nazi leader remarked to the British ambassador in Berlin, “I am an artist and not a politician. Once the Polish question is settled, I want to end my life as an artist.”