This hand-carved rock crystal ewer, made for the court of the Fatimid rulers of Cairo in the late 10th or early 11th centuries, is expected to fetch more than $5 million when it is auctioned in London in October. (Christie's/Associated Press)

A 1,000-year-old crystal decanter — incorrectly classifed as a 19th-century wine pitcher earlier this year — will be put up for auction again this fall.

Christie's is expecting the rare Islamic artifact to sell at its Oct. 7 sale of Islamic and Indian art in London for upward of $5.4 million.

The rock crystal ewer dates from the late 10th or early 11th century, and is one of only seven similar vessels known to have survived the court of Cairo's Fatimid rulers.

When the dynasty was overthrown, its members were forced to sell their treasures, including the rare, exquisite ewers. Among the six others known in existence, one is held by London's Victoria and Albert Museum while another is in the collection of the Louvre in Paris.

The slim-necked ewer — painstakingly carved by hand from a single, massive, flawless piece of crystal by ancient artisans — was later embellished with gold in France during the mid-19th century.

In January, an auction house in southwest England had offered the ewer for sale for between about $180 and $360 after having identified it as a 19th-century French wine pitcher.

However, eagle-eyed collectors knew better and a bidding war pushed the price to about $399,000.

After the ewer was correctly identified, however, that sale was annulled.

"If it's genuine as they say it is, then it's a tremendous discovery," said Anna Contadini, an Islamic art expert at London's School of Oriental and African Studies.

"There are lots of carved rock crystal items that are not genuine — either fakes or copies made at a certain point in the 19th and early 20th centuries.

"If it is genuine, it is priceless."

With files from the Associated Press