The book owner, who bought it for five sterling pounds at a second hand book store, expects it to fetch as much as £20,000 at auction. She said the book is all about Britains foreign trade in the 17th century so it might appeal to anyone with a Brexit bent. Sarah Hickman, who bought the book nearly 20 years ago, said: "Its a little bit of magic, everyone hopes this happens to them." "I was extremely pleasantly surprised and lucky to have bought it," she said, noting the book is titled Englands Treasure by Forraign Trade by Thomas Mun. It was published in 1664 and explains how vital foreign trade was for England, even though the country was at war with the Spanish and the Dutch. Hickman said: "Having studied printing, I knew it was an original and in good condition and it was a handsome book. Its always been a reasonably valuable book but the seller didnt know how lucky for me." She said she forgot about the book until she was tidying her home in Faversham, southeast of London. Its listed with a guide price of £15,000 to £20,000, with a £12,000 reserve. Hickman found one version of the book had been sold at auction in London for about £3,500 three years ago and so she emailed Christies to find out more about it.