Glossary · Mechanism
Breguet overcoil
A raised, curved terminal curve on a flat hairspring that improves its concentric development.
Explanation
The Breguet overcoil is a hairspring whose outer coil is raised and curved inward over the plane of the spring, ending in a shaped terminal curve. It makes the spring breathe more concentrically, improving isochronism and positional performance. Long a mark of chronometer-grade work, it appears in most high-grade mechanical watches today.
In the object catalogue
Catalogued objects whose own source record mentions “Breguet overcoil”. The quoted line shows where; it is the seller’s or museum’s wording, not independent verification.
Component
Elgin No. 239 Veritas Hairspring and Balance Assembly
“This horological component comprises the hairspring and balance assembly identified by the source as originating from an Elgin No. 239 Veritas pocket watch movement. The source …”
Pocket watch
C. Dégallier and Ch. Grottendieck hunting case pocket watch
“This hunting case pocket watch, manufactured in Switzerland circa 1900, features a 750-grade yellow gold case and a gold cuvette. The watch is signed by the Swiss manufacturer C…”
Pocket watch
Dual time zone pocket watch with split-center seconds
“Balance spring: Blued steel Breguet overcoil”
Pocket watch
Jules Jurgensen Minute Repeating Chronograph
“This Jules Jurgensen pocket watch, serial number 14338, is a minute-repeating keyless chronograph crafted in 18k pink gold. The watch is housed in a four-body polished "bassine …”
Pocket watch
J. Ullmann & Co. Quarter-Repeating Pocket Watch
“This J. Ullmann & Co. quarter-repeating pocket watch, identified by movement number 17747 and case number 156, dates to approximately 1890. The firm maintained operations in La …”
Wristwatch
Omega Observatory Tourbillon Wrist Chronometer
“This Omega wrist chronometer, numbered 10595936, is built with a Caliber 30 I movement, which was one of 12 produced in 1947 for Geneva Observatory trials. The movement particip…”