An rare Chinese bronze water vessel thought to have been taken during the looting of Beijing's Summer Palace in 1860 has been discovered in Kent, southeast England.

The relic will go on sale at The Canterbury Auction Galleries on April 11 at an estimated price of 120,000 to 200,000 British pounds ($170,000 to $285,000).

According to Canterbury Auction Galleries, only six similar vessels, known as ying, are said to exist, and five of them are in museums.

China's State Administration of Cultural Heritage said in a statement that it is looking into the auction, adding that it opposes the sale and purchase of stolen cultural relics.

The vessel dates to the Western Zhou Dynasty (1027-771 BC). It is called the Tiger Ying because the spout and lid are both cast with models of the creature.

Three other later Qing Dynasty bronze works of art were also found by the auction's consultant in Chinese art, Alastair Gibson.

"When I was asked to view a small collection of Chinese bronzes in this unassuming house, I didn't imagine the door would open to an 1860s time capsule," he said. "The last thing I expected to find was this remarkable bronze."

Gibson said that there is nothing comparable to the Tiger Ying in today's market.

Only one ying has ever been offered at auction before and none of the five others known is modeled on what in Chinese art is considered the king of beasts and the most powerful animal for warding off evil, Gibson said.

A test on the pottery core of the handle and one foot was done in Oxford, determining the age of the bronze vessel to be between 2,200 and 3,500 years old.

The Summer Palace was looted and destroyed by British and French troops during the Second Opium War (1856-60).

Also discovered was an archive of notes and photographs relating to the war. The notes were written by Royal Marines Captain Harry Lewis Evans (1831-83), who fought in the war and was present at the looting.

After the campaign the bronzes and other works of art made their way to England and then spent the next 158 years in the possession of Captain Harry Evans and his family, passing four generations down to the present owner.

Hajni Elias, a Chinese art and cultural historian who helped research the Tiger Ying, described it as "special and unequaled".

Elias said that ying were used for containing water for cleansing at rituals and sacrificial ceremonies conducted to pay respect to a person's lineage and ancestors.

"We cannot underestimate the wealth and sophistication of the late Zhou culture that created such an outstanding bronze vessel," she said.

Canterbury Auction Galleries said the Evans family of Fronfelen hopes that the auction will allow the bronzes to be cherished by a new generation of collectors from around the world and that some might find their way back to collectors in China.

Over 150 years after the ransacking and destruction of the Summer Palace, there have been efforts from Beijing to recover the stolen relics.

In 2009, auction house Christie's was asked by China to withdraw two Qing Dynasty bronze animal heads, one depicting a rabbit and the other a rat, believed to have been taken from the Summer Palace, from its sale of Yves Saint Laurent's collection in Paris.

The Chinese Cultural Relics Society estimated that China had lost more than 10 million antiques since 1840, due to wartime looting and illegal excavations.