Watercolors and sketches attributed to Adolf Hitler are up for sale Tuesday, forcing a tiny auction house in southwest England to install multiple telephone lines to accommodate an expected crush of bidders from Canada to New Zealand.

The 21 watercolors and two sketches were found in a farmhouse in Belgium, not far from where Hitler, then an aspiring artist, was stationed in Flanders during World War I.

The anonymous owners of the works, mostly landscapes, had the paper tested to determine its age, confirmed the signature and matched landmarks in the paintings to sites where Hitler was posted, said Chris Walton, a spokesman for Jefferys Auctioneers at Lostwithiel in Cornwall.

Still, it is impossible to say with certainty whether Hitler painted them. The experts who authenticated them in the 1980s are now dead. Even so, the works could sell for up to $8,000 apiece, Walton said.

“Some people would consider the sale somewhat controversial, but the pieces were executed so long ago, nearly 100 years ago, that they now just represent something of the past,” Walton said. “The paintings are of historical interest rather than artistic merit.”

Hitler is thought to have painted hundreds of pieces before becoming Nazi leader. His paintings have sold for up to $50,000.