IWC 89

Probable

The Mark XI's caliber, and the reason the watch met the Air Ministry's navigation specification: it hacks, so it can be synchronised to a time signal, which a navigator's watch must do. That is a functional test an examiner can run — pulling the crown should stop the seconds hand dead. A calibre 89 that does not hack is either faulty or not what it claims to be.

Specifications

Movement manufacturer: IWC
Production: 1946–?
Winding: manual
Complications: Centre seconds · Hacking seconds

Architecture

Manually wound centre-seconds caliber with a Breguet hairspring, used through the 1940s and 1950s including in the Mark XI supplied to the Royal Air Force.

Service practice

Service-issued watches were maintained by the service's own workshops, not by IWC, and were routinely rebuilt with whatever parts were held. Mixed period-correct components inside a military Mark XI are expected and are part of its history rather than a finding against it.

References using this caliber

IWC 6B/346Factory
Pilot's Watches · Whole production

Provenance of this record

Sources & Evidence

Secondary sourcePhysical examination

Research on IWC military-issued watches and Air Ministry markings

Institutional and collector research over issued examples

Accessed: 2026-08-18

Cited for

This referenceProbable

Secondary sourceCollector research

Ranfft Watch Movement Archive

Dr. Roland Ranfft (archived and maintained by volunteers)

Accessed: 2026-08-18

Cited for

This referenceProbable

View source ↗

Last verified: Not yet reviewed