A butterfly clasp is a strap fastening with two hinges that opens out to both sides, like a pair of wings. Opened, it makes the strap wide enough to slip over the hand.
How does a butterfly clasp work?
The clasp has two hinged parts shaped like wings. To take the watch off, press the release buttons on either side of the clasp. Both wings then spread apart, and the strap comes open in two directions at once. Because there are two hinges, the opened strap gets roughly 8 cm longer. That is enough for the watch to slide over the hand. The strap’s fitted length never changes, so it closes back to the same size each time.
Where is a butterfly clasp used?
Butterfly clasps are mostly found on integrated metal bracelets. There, the clasp hides the fastening almost completely and gives the bracelet a sleek look. Watches from Omega, Jaeger-LeCoultre and Oris use it. The name describes what happens when it opens. Two wing-shaped parts spread out to either side, much like the wings of a butterfly.
Not to be confused with
A standard deployant clasp also folds open, but it sits on the outside of the strap, where it can be seen. A butterfly clasp closes completely on the underside, so the band looks unbroken from above. Both types come in push-button versions. The word deployant comes from French and means to unfold or spread out.
Where it comes from
The butterfly clasp is credited to Louis Cartier. He also invented the deployant clasp, its predecessor, and developed the butterfly version for leather straps after it. Cartier’s deployant, made with Edmond Jaeger, was called the boucle déployante. It first appeared on the Cartier Santos in 1911. So the butterfly clasp grew out of an earlier folding design.
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