Fortis Cosmonaut Official Cosmonauts Chronograph Monolith

Reference 638.18.31

About this watch

The Fortis 638.18.31 is a robust tool that combines functionality, style, and a sprinkle of space adventure. This Swiss brand has carved out a niche for itself in the universe of aviation and space watches, so it’s no surprise that they’ve been the official timekeeper for astronauts. The watch features a sleek black PVD coating, Arabic numeral indexes, and stick hands ensuring readability. It's powered by the ETA caliber 7750, an automatic movement renowned for its reliability and precision. With a water resistance of 200 meters, this watch is more than capable of handling aquatic adventures. Its closed back adds a touch of mystery to the watch, allowing the external beauty to shine without revealing too much inside. The Fortis 638.18.31 features a lug width of 20 mm, making it versatile enough for both adventurous outings and formal occasions.
Buy Now on Jomashop
This is an affiliate link

Key Features

  • Automatic ETA movement with 25 jewels and 42-hour power reserve
  • 200m water resistance for aquatic adventures
  • Rotating bezel with 0-60 scale for tracking elapsed time underwater
  • Black PVD coating for a sleek, modern look
  • Arabic numeral indexes and stick hands for readability
  • Robust and durable design for everyday wear

Specifications

Brand
Fortis
Family
Cosmonaut
Model
Official Cosmonauts Chronograph Monolith
Reference
638.18.31
Movement
7750
Movement Features
  • Hours, Minutes, Small Seconds
  • Date, Day
  • Chronograph
Case
Stainless Steel 42mm
Dial Color
Black
Crystal
Sapphire
Water Resistance
200

Current Listings

[WTS] Vintage Fortis 610.22.158.1 Official Cosmonauts Blue Fume Dial Automatic Watch - $695

Vintage Fortis 610.22.158.1 Official Cosmonauts Blue Fume Dial Automatic Watch - $695

Fortis - 610.22.158.1 · $695
This Vintage Fortis 610.22.158.1 Official Cosmonauts Watch features a Mechanical (Automatic) movement and comes with a Fortis leather strap. The watch has been recently serviced, with some scratching on the Anti-Reflection coating of the crystal.

  • Condition: Used
  • Movement type: Mechanical (Automatic)
  • Straps: Fortis leather
  • Box: Generic
Posted at
Jun 18, 2025, 9:47 PM
Active
[WTS] Fortis Cosmonauts Chronograph 602.22.142 Extras $1790

Fortis Cosmonauts Chronograph 602.22.142 Extras $1790

Fortis - 602.22.142 · $1,790
A Fortis Cosmonauts Chronograph, issued for the Russian Cosmonauts Agency, featuring a Lemania 5100 chronograph movement and a sandblasted stainless steel case. The watch has a black matte dial with cream roman numerals and tritium lume.

  • Condition: great condition, signs of wear but no deep dings or scratches
  • Case dimensions: 38mm diameter, 20mm lug width, 46mm lug-to-lug, 13.75mm thickness
  • Movement type: Lemania 5100 chronograph movement
  • Strap material: brand new light brown 20mm genuine leather made by Fluco
Posted at
Jun 16, 2025, 9:37 AM
Active
[WTS] Fortis Cosmonauts Chronograph 602.22.142 Extras $1800

Fortis Cosmonauts Chronograph 602.22.142 Extras $1800

Fortis - 602.22.142 · $1,800
A Fortis Cosmonauts Chronograph with a sandblasted stainless steel case and a black matte dial, powered by the Lemania 5100 chronograph movement.

  • Condition: Great condition
  • Case Dimensions: 38mm diameter, 46mm lug-to-lug, 13.75mm thickness
  • Lug Width: 20mm
  • Movement: Lemania 5100 chronograph movement
Posted at
Jun 9, 2025, 9:23 AM
Active