A 14-foot painting from 2009 by infamous British artist Banksy will be hitting the auction block at Sotheby’s in London next month with a presale estimate of £1.5 million to £2 million ($1.9 million to $2.5 million), potentially breaking the artist’s current auction record of $1.9 million, also set at Sotheby in 2008. But some sleuths spotted strange inconsistencies between the painting Sotheby’s is offering and images of it from a decade ago.

The painting in question is titled Devolved Parliament (2009) and depicts the U.K.’s House of Commons run entirely by chimpanzees; the work was first shown in 2009 at the Bristol Museum & Art Gallery under the title Question Time, before being bought by a private collector in 2011. Despite the Sotheby’s catalogue entry for the work not originally mentioning it, Banksy aficionados have pointed out some differences in the painting as it appears now compared to when it was first shown. Though Banksy’s authentication bureau Pest Control has deemed the work to be the same painting previously displayed, these differences have left some viewers wary.

What are the differences?

• Most notably, in the 2009 iteration, the painting featured two large chandeliers illuminating the parliamentary chamber from the top of the canvas. These chandeliers have since disappeared and the surrounding areas have darkened.
• In 2009, a chimpanzee in the bottom left of the composition held an upturned banana. Though the chimpanzee has not changed, his banana now inexplicably faces downward.
• Two decorative carved wooden elements of the parliamentary benches, one in front of the newly downturned banana and one directly across from it, have been changed slightly.

What do these subtle changes in the painting signify, how do they affect the work’s provenance, and what does it mean that Sotheby’s didn’t mention them? In an email exchange with the New York Times, Sotheby’s acknowledged the differences, saying, “This work was first created in 2009. [. . .] When, that same year, it was first exhibited at the Bristol Museum, it carried the title Question Time. Since then, the painting has been reworked by the artist and more recently retitled.” The auction house’s online catalogue originally only specified that it was signed “09” and “acquired from [the artist] by the present owner in 2011.” Sotheby’s confirmed to the Times that it knew about the alterations, but did not tell the paper why it made the highly unusual decision not to mention them in the original catalogue entry. In a statement to Artsy, Sotheby’s said:

We were aware of the changes, and knew from the certificate of authenticity that this is the same work as was exhibited at Bristol Museum in 2009. References to these changes were added to our online catalogue following confirmation from the artist’s authentication body.

Ironically, Banksy’s last anti-market stunt (in which the artist shredded his own work after it sold for $1.3 million) helped propel his market value to its current level. We don’t know when or why the changes to Devolved Parliament were made, but they could be read as a similar, though far more subtle, gesture.

Clarification: An earlier version of this article did not include information that Sotheby’s had updated the catalogue entry for Banksy’s Devolved Parliament (2009) to acknowledge the changes made by the artist. The article has been revised to reflect this update and include a statement from the auction house.