British confectionery giants Cadbury, Fry and Rowntrees manufactured chocolate batches in 1900 to boost morale for soldiers fighting in the Second Boer War in South Africa, although it's not certain which company made this particular tin.
The bar and helmet belonged to the 8th Baronet Henry Edward Paston-Bedingfeld, who fought in the war, said the National Trust in a press release this week.
"Although it no longer looks appetising and is well past its use by date -- you wouldn't want it as your Easter treat -- it is still complete and a remarkable find," said Anna Forrest, the National Trust's cultural heritage curator. "We can only assume that the 8th Baronet kept the chocolate with the helmet as a memento of his time in the Boer War."