William Koch, perhaps best known in recent news for getting really, really upset after he was swindled out of millions of dollars by notorious wine forger Rudy Kurniawan (see Koch Brother Loses It On Air After Blowing Millions on Bogus Wine), is parting ways with more than 65 paintings depicting the American West.

The works, worth at an estimated $13 million, will be auctioned off on May 21 at “Visions of the West: American Paintings from the William I. Koch Collection,” a single owner sale at Christie’s New York.

Despite their seemingly limitless wealth (see Forbes’s 2015 Ranking of Billionaires Features Art Players Aplenty), the Koch brothers haven’t been able to buy good press over the past year. In addition to Bill’s teary-eyed 20/20 interview, in which he was totally overcome by his deep-passion for rare wines, brother David has twice sparked protests in recent months.

Demonstrators crashed the September opening of the Metropolitan Museum of Art‘s new $65 million David H. Koch Plaza in New York (see Protesters Crash Koch Plaza Opening at the Met and NYPD Detains Activists for Anti-Koch Light Graffiti at the Met). The mobile Natural History Museum, a project from arts collective Not an Alternative, sent an open letter encouraging the American Museum of Natural History in New York and the Smithsonian Institution‘s National Museum of Natural History in Washington, DC, to stop accepting his money (see Scientists Tell Natural History Museums to Shun Billionaire Donor and Climate Change–Denier David Koch).

As unpopular as the Koch brothers are, it remains to be seen if their political leanings and perceived “evil billionaire” ways will taint the upcoming auction. There are plenty of people who would think twice about adding to the Koch coffers, but blue-chip art collectors seem unlikely to be among their number.

The auction’s offerings will range from late 19th-century works to the present day, with artworks by important historic artists of the American West such as Thomas Moran, Frederic Remington, Henry F. Farny, William Robinson Leigh, and Philip R. Goodwin. Among the contemporary artists featured are Howard Terpning, Martin Grelle, Tom Lovell, and G. Harvey.