A newly-discovered Faberge egg featuring a mechanical, diamond-encrusted cockerel is expected to fetch up to $20 million when it's put on the block at a London auction in November.

"The discovery of this masterpiece is the most exciting of my 40-year career," said Anthony Philips, international director of Russian works of art at Christie's auction house.

The Rothschild Faberge Egg, with a cockerel that pops up every hour to crow, is on display at Christie's auction house in London.
(Sant Tan/ Associated Press)

"We expect this remarkable object to be of profound interest to private collectors and institutions from around the world."

The egg, made in 1902 by Peter Carl Faberge, is a rare find, one of only three known Faberge items featuring a clock and a mechanical figure. The cockerel pops out every hour to flap its wings, bob its head and crow.

The egg, made for the Rothschild banking family, has been described as unusually large and enameled in pink with gold detailing.

Faberge was a Russian jeweller whose exquisite craftsmanship lives on in the 50 eggs he made for the Russian royal family. He created another dozen for private clients.

Czar Alexander III commissioned the first as an anniversary present for his wife, Empress Maria Fedorovna, on Easter Day 1885. She became so captivated with the enameled item that the czar ordered one made for her every Easter.

After the czar died in 1894, his son Nicholas continued the tradition until the Russian Revolution in 1917. Nicholas and his family were executed in 1918.

Many of Faberge's creations have found their way into Western collections.

With files from the Associated Press