The perfectly-preserved sweets were made by Cadbury to celebrate the coronation of King Edward VII and Queen Alexandra in 1902.

They were given to nine-year-old Mary Ann Blackmore at her school that year, but instead of eating them, she decided to keep them as a memento of the occasion.

The vanilla chocolates were passed down through her family until her granddaughter, Jean Thompson, 72, brought the tin to Hanson's Auctioneers in Derby.

Morven Fairlie, of Hansons Auctioneers, said: "Back in that time, this was a real treat, children never got chocolate.

"It was obviously such a special gift to this little girl that she thought she couldn't even touch it."

The chocolates will be auctioned at Hansons and are expected to fetch at least £100 to £150.

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Mrs Fairlie said: "It may make more, sometimes you get a few bidders, people who want a piece of history, and the price could rocket.

"It depends on who collects royal memorabilia, and who wants to collect things from this time."

The 121-year-old chocolates have far passed their use-by date.

"Nobody's going to be eating it," Mrs Farlie added.

"If you do open the tin, it does smell of chocolate, but I wouldn't want to risk it."