A hitherto unrecorded architectural clock attributed to famed horologist Samuel Knibb is expected to make £200,000 ($306,430) at Bonhams on July 9.
The Knibb-signed clock is one of only five known examples.
Bonhams' clock expert James Stratton comments: "When an email arrived entitled 'Samuel Knibb' I was immediately intrigued.
"Samuel Knibb's work is incredibly rare - I only knew of four clocks by him; three in private collections and one in the Clockmakers Company museum in the Guildhall, London. But within minutes of opening up the images, it was obvious that this example was an absolutely genuine example from his workshop.
"It is so exciting to offer this previously unrecorded clock to the market this summer after 350 years in hiding - it will offer collectors and curators the world over the chance to learn more about one of the great 'unsung' horological heroes of the early age."
Known as the "Clockmakers of Claydon", the Knibb family (comprising brothers John and Joseph Knibb and their cousin Samuel) gained international renown within their lifetimes.
Genuine Knibb clocks seldom come to market. In October 2004, a Joseph Knibb-signed longcase clock sold for $540,000 at Sotheby's New York.
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