A 100-year-old watercolor of Munich's old city hall is expected to fetch at least £40,000 at auction this weekend - not so much for its artistic value as for the signature in the bottom left corner reading A. Hitler.

The painting is one of some 2,000 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.

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

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The 100-year-old watercolor of Munich's old city hall is expected to fetch at least £40,000 at auction

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

Though Hitler's paintings surface fairly regularly, Ms Weidler said this 11x8.5 inch scene, unimaginatively called 'The Old City Hall,' is particularly valuable.

It 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.

The starting price for the painting is about £3,600, and the auction house, which has sold several Hitlers over the past decade, expects it will go for £40,000 - but would not be surprised if sold for double that

The watercolour includes the original bill of sale and a signed letter from Hitler's adjutant, Albert Bormann, brother of Hitler's private secretary Martin Bormann

Hitler as a young man during his stay in a military hospital

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

The starting price is about £3,600, and Weidler, whose auction house has sold several Hitlers over the past decade, said she expects it will go for £40,000 - 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.'

The painting is one of some 2,000 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