The work, which had been kept in a box of drawings by a French family of bibliophiles, was discovered by Thaddée Prate of the Paris auction firm, who then consulted the Paris expert Patrick de Bayser.
The double-sided sheet depicts Saint Sebastian tied to the trunk of a tree to one side and two scientific sketches to the other. The attribution to Leonardo has been confirmed by Doctor Carmen C Bambach, curator of prints and drawings at the Metropolitan Museum in New York.
When the discovery was announced two years ago, a date was set to auction the drawing in June 2017 but the work was then declared a national treasure, meaning that it could not be offered for 30 months to allow a national museum the opportunity to acquire it.
With that time now elapsed, the work can go under the hammer and the date has been set for June 19, 2019, at Tajan saleroom in Paris.
The drawing has an ‘estimate on request’ of around €15m-20m but, the auction house observed, since the Leonardo painting Salvator Mundi was sold by Christie’s last year for a premium-inclusive $450m, it could make much more.