The J. Paul Getty Museum in Los Angeles has just announced a major purchase of 16 Old Master drawings and one 18th-century painting, all from a British private collection.

The museum calls it the most important acquisition in the history of its drawings department, but it also likely ranks as one of the institution’s largest ever, reportedly worth upwards of $100 million. Today, the endowment at the Getty reportedly stands at a hefty $6.5 billion.

The latest deal includes drawings by Michelangelo, Lorenzo de Credi, Andrea del Sarto, Parmigianino, Rubens, Barocci, Goya, Degas, and others. The deal also includes a painting by Antoine Watteau called La Surprise. The masterpiece had been missing for more than 150 years before it resurfaced in 2007, Christopher Knight reported in the  Los Angeles Times.

L: Andrea del Sarto’s Head of Saint Joseph (c.1526–1527). R: Michelangelo’s Study of a Mourning Woman (c.01500–1505). Images courtesy of the J. Paul Getty Museum.

Getty director Timothy Potts described the addition of these new works as “truly a transformative event in the history of the Getty Museum,” adding that “it is very unlikely that there will ever be another opportunity to elevate so significantly our representation of these artists, and, more importantly, the status of the Getty collection overall.”

The Watteau scene ranks as the most expensive work by the artist ever sold at auction. According to the artnet Price Database, it sold at Christie’s London in 2008—one year after it was rediscovered—for £12.4 million ($24 million), soaring past its £3 million-to-£5 million estimate. The painting features a young couple locked in a passionate embrace, completely oblivious to a nearby musician named Mezzetin, a.k.a. the trouble maker. So-called “commedia dell’arte” figures feature prominently in the work of Watteau, who died in 1721 at the age of 27.

Meanwhile, the Michelangelo sold at auction for $7.7 million in 2001 and del Sarto’s Head of Saint Joseph, sold for £6.5 million ($11.4 million) at Christie’s London in 2005.

John Martin’s The Destruction of Pharaoh’s Host (1836). Image courtesy of the J. Paul Getty Museum.

Export licenses, allowing the works to leave the UK, have been granted for all but four of the drawings. In cases where works are historically important, an export license can be temporarily declined while a local buyer is sought to meet an agreed price.

The recent addition of Old Master drawings is the latest high-profile buy for the institution. As reported by artnet News in November 2014, the Getty was the buyer of one of two blockbusters at Christie’s New York evening sale, when it shelled out $65.1 million for Edouard Manet’s Le Printemps (1881).

Edgar Degas’s After the Bath (c.1886). Image courtesy of the J. Paul Getty Museum.