A 100-year-old watercolour of Munich’s old city hall is expected to fetch at least 50,000 euros ($A75,000) at auction this weekend, not so much for its artistic value as for the signature in the bottom left corner: A. Hitler.

Nuremberg’s Weidler auction house says the painting is one about 2000 painted by Adolf Hitler and is thought to be from about 1914, when he was struggling to make a living as an artist, almost two decades before rising to power as the Nazi dictator.

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It has drawn interest from around the world, with most viewing it as a curiosity or as an investment, said auction house director Kathrin Weidler.

It’s being sold by a pair of elderly sisters, whose grandfather purchased the painting in 1916.

Though Hitler’s paintings surface fairly regularly, Weidler said this 28×22 cm (11×8.5 inch) scene, unimaginatively called “The Old City Hall”, also includes the original bill of sale and a signed letter from Hitler’s adjutant, Albert Bormann, brother of Hitler’s private secretary Martin Bormann.

From the text of the undated Bormann letter, it appears the Nazi-era owner sent a photo of the painting to Hitler’s office asking about its provenance.

Bormann wrote back that it appears to be “one of the works of the Fuehrer”.

The starting price is 4500 euros ($A6750), and Weidler, whose auction house has sold several Hitlers over the past decade, said she expects it will go for 50,000 euros – but wouldn’t be surprised if sold for double that.

If it does, however, it will be because of the name in the corner alone, she said.

“It’s perfectly well done, but I’d rate its artistic value as fairly minimal.”