Two pieces of Agatha Christie's jewellery, both encrusted with diamonds, are up for auction at Bonhams London on October 8.
An engagement ring, thought to have belonged to the writer's mother, is valued at ?�3,000-5,000 ($5,028-8,380), while a brooch is estimated at ?�6,000-8,000 ($10,000-13,408).
The consignor, Jennifer Grant, discovered the pieces in a locked box that she bought at the clearance of Greenway, Agatha Christie's house in Devon, in 2006 for just ?�100 ($167).
She commented: "I was thrilled to have stumbled upon my very own mystery. I always wondered what was locked inside the strongbox but I never dreamt it would be anything so exciting as diamonds - I could hardly breathe when I unwrapped the tissue paper and found them.
"As an Agatha Christie fan, it's wonderful to think that these items actually touched her life.
"I've enjoyed the jewellery greatly over the last four years but I don't wear it as much as it deserves. I thought - why not let someone else enjoy them."
A first edition copy of Christie's Poirot Investigates sold for ?�34,000 ($57,050) at Dominic Winter Book Auctions in 2012.
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