(The Met said it had no agreement with the auction house to buy or to show the artwork.)

According to Dr. Bambach, the drawing — which she hopes will be bought by a French museum — represents the first “Leonardo, full stop” discovery (as she put it) in this medium since 2000, when Sotheby’s in London offered a slighter sheet from around 1506 to 1508 that had black chalk and pen studies of Hercules and whirlpools. It failed to sell against a low estimate of 400,000 pounds, or what was then about $600,000, but sold later for about $550,000. The drawing (also attributed by Dr. Bambach) is now jointly owned by the Metropolitan Museum of Art and the New York collector Leon Black and his wife, Debra Ressler.

As for a much-debated mixed-media profile portrait of a young woman, known as “La Bella Principessa,” which eight years ago was valued by the London dealer Simon Dickinson at as much as $150 million, Dr. Bambach commented, “It does not look like a Leonardo.”

A painter, sculptor, architect, scientist and inventor of seemingly limitless ambition (if not finished execution), Leonardo (1452-1519) most formidably embodies the notion of universal genius. This reputation has been translated into formidable financial value for the few of his works that have come up for sale. In 1994, Bill Gates paid $30.8 million at Christie’s for the “Codex Hammer” notebook, containing 300 drawings and scientific writings. More controversially, in 2013 the Russian billionaire Dmitry Rybolovlev bought Leonardo’s painting “Christ as Salvator Mundi,” circa 1499, for $127.5 million from the Swiss businessman and dealer Yves Bouvier, who had recently bought it for $80 million from a consortium of dealers. The current high for a Leonardo drawing sold at auction is $11.5 million, at Christie’s in 2001, for a silverpoint study of a horse and rider.