Head of a Muse by Raphael

Two masterpieces by Rembrandt and Raphael went on public display Friday for the first time in decades, ahead of a major auction of Old Masters and 19th century art at Christie's in London.

A painting by Rembrandt held in private for the last 40 years, “Portrait of a man, half-length, with his arms akimbo,” is expected to sell for between 18 and 25 million pounds (30 to 40 million U.S. dollars, 20 to 28 million euros).

Meanwhile Raphael's “Head of a Muse,” a drawing seen only once in public in the last 50 years and not put up for general auction for more than 150 years, is estimated at between 12 and 16 million pounds.

They will form the highlight of the Christie's sale on Tuesday, which will see a total of 43 works worth between 44.9 and 62.6 million pounds auctioned.

Also among them will be “Saint John the Evangelist” by Domenichino, described as “one of the most important Baroque paintings to be presented at auction in a generation” and estimated at between seven and 10 million pounds.

Richard Knight, international co-head of Old Masters and 19th century art at Christie's, said the auction “promises to be a landmark sale.”

“We will offer important masterpieces by Rembrandt and Raphael — two of the most accomplished and celebrated artists in the history of art — as well as a monumental and exceptionally important painting by Domenichino,” he said.

Meanwhile, a “beautifully preserved” early work by Rubens, which has rarely been seen in public in its 400-year history, will go on sale at auction house Sotheby's on Wednesday with an estimate of four to six million pounds.

At the same event, the last known self-portrait by Anthony van Dyck will go on sale estimated at between two and three million pounds.