An antique diamond necklace worn at Queen Elizabeth II’s coronation and may be linked to a French scandal involving Marie Antoinette could fetch as much as £2m at auction.

The necklace, made of 300 carats, was also worn to King George VI’s coronation by members of the Marquess of Anglesey family, who owned the diamonds until the 1960s when they sold them.

It has not made a public appearance for half a century until now, and it is estimated to fetch a high price – between £1,348,416 and £2,097,536 when it is offered in the Sotheby’s Geneva sale in November.

The decadent necklace boasts 500 diamonds, featured on three ropes, and will go on a global tour beginning at Sotheby’s London auction house before jetting off to Hong Kong, New York, Singapore, Taipei and Dubai.

Some jewellery historians believe it features diamonds from the infamous piece that created a scandal for Marie Antoinette. The “affair of the necklace”, when the French queen was falsely accused of not paying for the item – which was really taken by a conman who pretended to be acting on her behalf.

Andres White Correal, the chair and head of the royal and noble sales at Sotheby’s for Europe and the Middle East, told the PA news agency: “I think the most important part, other than the value of the diamonds, is the fact that it has survived.

“You only see these things in museums when it has been from royal families who are still reigning, like the collections here in Britain, or when you go to former imperial and royal collections in places like St Petersburg or Moscow, where you can see the collections of the tsar.

“So yes, you go to a museum, and you can see a jewel of this level. Normally, you don’t see it in private hands.”

Correal said he hoped the necklace was acquired by an institution or for a private collection that “appreciates” the jewels and would allow the public to learn about their history and how people used to wear jewellery.

“And if that wouldn’t be the case, I would love for the necklace to go to a solid and wonderful collection where a person who appreciates this type of jewel would safe-keep it for the next generation,” he added.

“I don’t think that objects like this you actually own, you are merely the custodian of such an incredible object to pass it on, either to a new generation or to an institution where many other people can enjoy it.”

The necklace will be auctioned at Sotheby’s royal and noble sale on 11 November at the Mandarin Oriental in Geneva.