Speculation is afoot that Piero Manzoni's Merda d'Artista (a 1961 work in which Manzoni filled 90 30-gram cans with his faeces and then sold them as art, as a critique of the art market) might not be exactly what they seem.
In an article titled 'Solo gesso, nella scatoletta di Manzoni' published in Corriere della Sera (Italian) Agostino Bonalumi, who worked with Manzoni, claims that the tins are actually filled with plaster.
The problem: no one can confirm this without peeling open one - or all - of the tins. The tins, mind you, have a current market value of £81,000 (as paid at Sotheby's Milan last month).
Stuart Jeffries has posted on the Guardian arts blog about the conundrum, quoting a Tate spokesperson statement that "Keeping the viewer in suspense is part of the work's subversive humour." (The Tate purchased a can in 2000 for £22,350).