Secret weapons from World War II, including two prunes, sold for £2,700 when they went under the hammer.
The prunes were used to smuggle documents
Richard Marshall, from Crook, in County Durham, sold the memorabilia which belonged to his great-aunt, Doreen Mulot, a British agent.
The prunes had their stones removed and replaced with miniature maps or other documents which were smuggled to prisoners of war in occupied countries.
The lot had been expected to fetch £800 to £1,200 at London auctioneers Spink.
Doreen Mulot, was a former member of Britain's Special Operations Executive, which Churchill set up to carry out operations behind enemy lines.
She married a Frenchman, but returned to England in 1940, and helped the war effort.
Her great-nephew said that she and another woman prepared the prunes in a bathroom at her home in Hampstead.
He said: "As the prunes swelled up they carefully picked out the stones and filled the cavities with carefully rolled up maps of Europe covered in waxed paper.
"These prunes were then dried out and sent out in parcels to prisoners of war in occupied territories.
"The maps detailed the railway lines that criss-crossed across Europe and provided prisoners with the detail that they needed to effectively plan their escape."
The two prunes that were sold on Thursday, were kept by Doreen Mulot as mementos.
The lot also included printing plates to forge banknotes used in POW camps, small booklets containing instructions on sabotaging German facilities, and a hand-held roller used to print "Free French" slogans on walls.
Caroline Viner, a specialist at Spink, said it was unique material and there was nothing to compare to it.
She said: "It is just extraordinary that this sort of collection has survived, and we are very pleased and excited to have it in the auction."