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The Encyclopedia of Horology

Wristwatch · Tourbillon wristwatch

Audemars Piguet Tourbillon Automatique Ref. 25 643 BA

Partially verified

This Audemars Piguet Tourbillon Automatique, identified as number 186, is a self-winding gentleman's wristwatch featuring a vertical elliptical-shaped 18K yellow gold case measuring 35.2 x 28.7 mm. Produced circa 1990, the timepiece is powered by the extra-thin Calibre 2870 movement, which utilizes the inside of the case-back as the main-plate. The movement incorporates a one-minute tourbillon regulator, a titanium tourbillon carriage, and a platinum-iridium pendulum oscillating mass. Additional technical features include a going barrel, a lateral lever escapement, a Glucydur screw-balance, and a self-compensating flat hairspring. The dial is signed by the manufacturer, and the watch is fitted with an Audemars Piguet brown leather strap and an 18K yellow gold deployant clasp. The watch is presented with its original fitted box. Time setting is achieved via the back of the case.

Front view of the Audemars Piguet Tourbillon Automatique, showing the dial, tourbillon aperture, and leather strap.
Front view of the Audemars Piguet Tourbillon Automatique, showing the dial, tourbillon aperture, and leather strap. — Antiquorum. Rights pending — permission not yet requested. Original source

Catalogue identity

Source
catalog.antiquorum.swiss
Category
Wristwatch · Tourbillon wristwatch
Maker / attribution
Audemars Piguet
Reference
25 643 BA
Catalogue / lot identifier
437
Source-reported date
circa 1990
Source-reported place
Switzerland
Source-reported serial
186

Source-reported attribution and specifications are not independent authentication. A listing does not establish present ownership, current display, availability or permission to reproduce.

Object description

Case and Dial

The watch is housed in a vertical elliptical case crafted from 18K yellow gold, measuring 35.2 x 28.7 mm. The design includes a unique time-setting mechanism located on the back of the case rather than through a traditional crown.

The dial features a decorative radiating guilloche pattern with the Audemars Piguet signature. An aperture at the upper left position exposes the one-minute tourbillon regulator, while the lower section of the dial provides a view of the oscillating mass component.

Evidence for this section
  • “vertical elliptical-shaped, extra-thin, gentleman's wristwatch, with back time setting”
  • “a one-minute tourbillon regulator”

Movement and Construction

The movement is the extra-thin self-winding Calibre 2870. The construction is notable for using the inside of the case-back as the main-plate.

Technical components include a titanium tourbillon carriage and a platinum-iridium pendulum oscillating mass. The assembly also contains a lateral lever escapement, a Glucydur screw-balance, and a self-compensating flat hairspring.

Evidence for this section
  • “Calibre 2870, 32.8 x 27.8 mm., the inside case-back as main-plate”
  • “titanium tourbillon carriage and platinum-iridium pendulum oscillating mass”

Condition and Authenticity

The auction description reports the watch to be in excellent condition under their internal grading system, although the movement is noted as requiring an overhaul. The case exhibits minor surface wear.

The watch is accompanied by its original fitted box. Signatures are verified on the dial, case, and movement.

Evidence for this section
  • “Grading System Grade: AAA Excellent”
  • “Overhaul recommended, at buyer's expense”
  • “Signature dial, case and movement”

Open research questions

  • What is the specific production date range for the Calibre 2870 within the Reference 25 643 series?
  • Are there variations in the guilloche patterns observed on other examples of Reference 25 643?

Source evidence

Recorded claims and source quotations for Audemars Piguet Tourbillon Automatique Ref. 25 643 BA
FieldSource-reported valueSource quotation
MakerAudemars Piguet“Audemars Piguet”
Reference25 643 BA“Ref. 25 643 BA”
Movement Serial186“Movement No. 186”
Yearcirca 1990“Year circa 1990”
Case Material18K yellow gold“18K yellow gold, self-winding, vertical elliptical-shaped”
Calibre2870“Calibre 2870”
Dimensions35.2 x 28.7 mm“35.2 x 28.7 mm”
FunctionsOne-minute tourbillon, self-winding“a one-minute tourbillon regulator”

Visible details

  • Vertical elliptical-shaped yellow gold case
  • Visible tourbillon cage positioned at the upper left of the dial
  • Guilloche radiating pattern on the dial surface
  • Signed Audemars Piguet on the dial

Research qualifications

  • Condition of the movement is described as needing an overhaul
  • General grading system reports slight scratches on the case

Photograph identity and source facts were screened before import; rights clearance remains pending.

Consulted source

AUDEMARS PIGUET "TOURBILLON AUTOMATIQUE" IN 18K YELLOW GOLD NO. 186

Reviewed 2026-10-26 · Record 2f443554be

Terms in this record

Glossary explanations for terms named in this object’s record.

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