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The Encyclopedia of Horology

Wristwatch · Chronograph

Minerva Cal. 13-20 Chronograph, Frey Era

Partially verified

This vintage Minerva chronograph wristwatch is documented as dating from the Frey family ownership era of the manufacture. The piece is fitted with calibre 13-20, an architecture later adapted into calibre 13-21, housed in a 37 mm metallic case. The dial displays two oversized engine-turned subsidiary counters at 3 and 9 o'clock that partially interrupt the gilt Arabic hour markers at 2, 4, 8, and 10. The dial is signed 'Minerva INCABLOC' and marked 'SWISS' at 6 o'clock. According to the source, the first owner had a display case back installed to view the movement.

Dial and case view of the Minerva Cal. 13-20 chronograph on a textured light blue leather strap
Dial and case view of the Minerva Cal. 13-20 chronograph on a textured light blue leather strap — KMII. Rights pending — permission not yet requested. Original source

Catalogue identity

Source
www.watchprosite.com
Category
Wristwatch · Chronograph
Maker / attribution
Minerva
Reference
Not recorded
Catalogue / lot identifier
Source URL identifies the listing
Source-reported date
Not established
Country
Switzerland

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

Dial Configuration and Hands

The watch displays a cream dial featuring gilt applied Arabic numerals, bordered by an outer track divided into seconds and fifths of a second. Time is indicated by gilt leaf-style hour and minute hands accompanied by a central chronograph seconds hand. Directly below the 12 o'clock hour marker, the dial is signed 'Minerva INCABLOC', and 'SWISS' is printed along the bottom boundary below 6 o'clock.

The dial layout incorporates two oversized snailed subsidiary counters: a running seconds register at 9 o'clock and a 30-minute chronograph counter at 3 o'clock. The dimensions of these registers cut into several of the Arabic numerals along the dial's horizontal axis, partially interrupting the numerals at the 2, 4, 8, and 10 positions.

Evidence for this section
  • “Two large snailed subsidiary dials: running seconds at 9 o'clock and a 30-minute register at 3 o'clock”
  • “Admittedly it results in some cut numerals but also in very large - relatively speaking - subdials and hence great usability in terms of the chrono function.”
  • “Dial signature below 12 reads 'Minerva INCABLOC' and 'SWISS' is printed at the bottom edge beneath 6 o'clock”

Case Architecture and Mounting

The timepiece is encased in a polished metallic case measuring 37 mm in diameter. The case features down-turned lugs, a fluted winding crown, and rectangular pushers positioned at 2 and 4 o'clock to operate the chronograph mechanism.

The watch is shown fitted with a textured light blue leather strap that features tone-on-tone edge stitching. The specific metal alloy of the case is not documented in the provided source.

Evidence for this section
  • “smaller 37mm case”
  • “Polished metallic case with down-turned lugs, a fluted winding crown, and rectangular chronograph pushers”
  • “Mounted on a textured light blue leather strap with tone-on-tone edge stitching”

Reported Movement and Modifications

The watch is identified by the source as housing the Minerva calibre 13-20, an architecture noted to be dimensionally similar to the modern calibre 13-21. Dating to the Frey ownership era, the movement is reported to feature functional finishing rather than the higher decoration associated with later periods such as the Gnutti era.

The source reports that an aftermarket display case back was installed by the original owner. However, neither the movement itself nor the rear of the case is depicted in the supplied photograph.

Evidence for this section
  • “The Cal.13-20 chronograph is from the swan-song era of the Frey ownership of the brand”
  • “size wise very much the same at the currently used 13-21”
  • “even though the first owner got a display case back installed, the finishing of the movement is nowhere near as exquisite as introduced during the Gnutti era”

Open research questions

  • What specific alloy comprises the 37 mm case (e.g., stainless steel, chrome-plated base metal)?
  • Is the original solid case back preserved alongside the reported aftermarket display back?
  • What serial numbers and reference markings are stamped on the calibre and inside the case back?

Source evidence

Recorded claims and source quotations for Minerva Cal. 13-20 Chronograph, Frey Era
FieldSource-reported valueSource quotation
Movement CalibreCal. 13-20“The Cal.13-20 chronograph is from the swan-song era of the Frey ownership of the brand”
Case Diameter37mm“smaller 37mm case”
Production EraFrey ownership era“from the Frey era, a period when Minerva was a true manufacture”
Shock Protection MarkingINCABLOC“The Incabloc Minerva chronograph, particularly the Cal. 13-20”
Case Back AlterationDisplay case back installed by first owner“the first owner got a display case back installed”

Visible details

  • Cream dial with outer seconds and fifths-of-a-second track and gilt applied Arabic numerals
  • Two large snailed subsidiary dials: running seconds at 9 o'clock and a 30-minute register at 3 o'clock
  • Gilt leaf-style hour and minute hands with a central chronograph seconds hand
  • Dial signature below 12 reads 'Minerva INCABLOC' and 'SWISS' is printed at the bottom edge beneath 6 o'clock
  • Polished metallic case with down-turned lugs, a fluted winding crown, and rectangular chronograph pushers
  • Mounted on a textured light blue leather strap with tone-on-tone edge stitching

Research qualifications

  • The movement and the aftermarket display case back mentioned in the text are not shown in the single dial photograph.
  • Reference number and exact year of manufacture are not stated in the source text.

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

Consulted source

Minerva Cal. 13-20 Chronograph Frey Era — WatchProSite Forum Digest

Reviewed 2026-10-21 · Record fa343f12e9

Terms in this record

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

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