A Swiss automaton displaying two singing birds is expected to make $411,000-825,000 at Sotheby's Geneva on May 14.
The piece was designed and built by Jean-David Maillardet, a member of a famous family of automaton builders, in the late 18th or early 19th century.
Pedro Reiser, department manager of Sotheby's watch division in Geneva, comments: "This wonderful automaton is a rare find - all the more exceptional because it features an automated butterfly.
"Records suggest that only one other double-bird cage clock with an automaton butterfly is currently known."
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