A newly discovered Mantegna drawing will be offered at Sotheby’s Old Masters sales.

A recently discovered Andrea Mantegna drawing, said to be the only known study for one of his canvases in the Triumphs of Caesar (late 15th century), will be offered at Sotheby’s this January. The work has been estimated to sell for over $12 million in Sotheby’s Old Master Drawings auction.

The Triumphs of Caesar is Andrea Mantegna’s best known work, and consists of nine canvases depicting Julius Caesar and his army processing through Rome. The Sotheby’s drawing is a study for the second canvas in the Triumphs series, The Standard Bearers and the Siege Equipment. It depicts statues on carts, large siege weapons, and a model of the tower of Alexandria. Of Mantegna’s roughly 20 known drawings, it’s believed that all but two are in the collections of major museums.

The drawing has been dated to the late 1480s, and was sold in 1885 as a drawing attributed to Mantegna. It then disappeared into private collections until shortly before the “Mantegna and Bellini” exhibition in London and Berlin earlier this year. Cristiana Romalli, senior director and Italian specialist in the Sotheby’s Old Masters Drawings Department, said she was able to definitively attribute the drawing to Mantegna through infrared analysis, which revealed a significant alteration of the drawing during its creation. Sotheby’s says this change conclusively proves that Mantegna authored the drawing, and sheds light on his creative process.

Romalli said of the drawing:

The discovery of a previously unseen underdrawing, more than five hundred years after it was made, is a moment of considerable importance for the study of this complex, intriguing and highly influential master of the early Italian Renaissance. [...] The exceptional and rare opportunity to bring to light this news, obscured for centuries, is what defines the excitement and thrill of the drawings market.