The gemstone-crusted necklace which is valued at between $150,000 and $200,000 was one of Evita's favourite pieces of jewellery.

It will go under the hammer on 15 October, Christie's said on Thursday.

The legendary former first lady, who died in 1952, sported the necklace in official portraits and is also pictured wearing the gems in stamps from the period.

Still intact

The necklace is made in a Victorian style of the 19th century, and its survival is unusual as most necklaces from this period have parted company with their rare gems.

"It was very typical during the 19th century when there were important stones in a piece that those pieces would be dismantled so the stones could be reused," explained Christie's spokeswoman Katherine Adler.

The necklace's rarity is enhanced by the fact it is inset with rough Burmese rubies, usually such precious gems are treated to improve their colour or purity.

Evita's stones have not been tampered with

Shady lineage

"The fact that this piece has remained intact is quite weird," Adler said.

However, she declined to identify the mystery owner of the necklace.

It was purchased six years after Evita's death in 1958 by a buyer whose identity remains a secret. It is also unknown how the gems came into Evita's possession.

Evita was married to former Argentine President Juan Domingo Peron who ruled the south American nation between 1946 and 1955 and from 1973 to 1974.