A tin of Cadbury chocolates more than a century old will go to auction soon after being perfectly preserved for 121 years.

The chocolates were originally given to a schoolgirl to celebrate the coronation of King Edward VII and Queen Alexandra on June 26 1902. Cadbury produced the special tins of vanilla chocolates to mark the event, with the two monarchs featuring on the front of the tin.

When nine-year-old Mary Ann Blackmore received the treat at her school in Durham in 1902, she decided not to eat the chocolate, and instead keep the tin and its contents as a token of the important royal event.

Since then, the chocolates have been passed down through the family’s generations, with the treats remaining untouched. It was Mary’s granddaughter, Jean Thompson, 72, who 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 have been estimated to reach at least £100 to £150.

“It depends on who collects royal memorabilia, and who wants to collect things from this time,” explained Mrs Fairlie.

“It may make more, sometimes you get a few bidders, people who want a piece of history, and the price could rocket.”

The 121-year-old chocolates have far passed their use-by date. “Nobody’s going to be eating it,” she added.

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

The coronation chocolates are expected to feature in Hansons’ July saleroom.