It was meant to be eaten well over a century ago.
But Queen Victoria's gift of a tin and bar of chocolate to a soldier serving in South Africa in the brutal Boer War of 1899 - 1902 was never consumed.
It might look as tasty as dried mud, but auctioneers are estimating it will fetch £50 to £300 when it goes under the hammer next Tuesday.
The chocolate they say, is probably the "most controversial chocolate" ever made - sparking a right Royal row that threatened to blacken the names of the country’s top chocolate makers.
Paul Cooper of Scunthorpe-based Eddisons CJM said: “In 1899 the Queen decided to cheer up her troops fighting in the war . . . which was going rather badly at the time . . . by personally paying for a gift tin of chocolate to be sent to every ordinary soldier.
“The problem was that all of the country’s top chocolate makers . . . Cadbury, Fry and Rowntree . . . were owned by Quakers.
"They were pacifists, opposed to the war and they were appalled by the idea of being seen to profit from the fighting.”
The manufacturers realised that refusing to comply would cause them immense reputational damage.
In the end they decided to donate the chocolate free of charge but unbranded and in tins that did not carry their names.
Mr Cooper said: "The Queen was not amused. She wanted the boys to know they were getting best British chocolate.
"The firms backed down again, sort of. Some of the chocolate was then marked but the tins never were.”
Last month their auction of 103-year-old chocolate bars sent to WW1 soldier Richard Bullimore attracted international headlines.
A lot including Mr Bullimore's Distinguished Conduct Medal fetched over £3,000.
It also sparked the attention of Tuesday's seller - a woman in London who thought she had even older chocolate.
She once owned a shop in Lincoln’s Inn Fields selling collectables and her chocolate had lingered in a cupboard for a quarter of the century.
Although the Queen's gift was ridiculed by the Continental media at the time, the soldiers loved their Royal gift.
Many sent their tins home unopened. Others turned down offers of £20 - despite only earning something like a shilling a day.
The auction catalogue is available at www.eddisonscjmasset.com or Bidspotter.co.uk.