Series 31

Serie 31


Serie 31

The instrument watch

Our Serie 31 is an instrumental manual winding watch with an indirect central second hand. The sapphire crystal directs the focus to the very readable face

360 View

Price: -- €

incl. VAT, free shipping within Germany
For dispatch to countries outside the EU, VAT won't be charged.
Unless otherwise specified the delivery time is approx. 2 weeks.
Kroko straps (reptile leather) cannot be shipped outside the EU

Series 31

The pocket watch movement that has been redesigned to feature an indirect central second hand makes this watch an elegant choice. A key feature of the movement remains the secret of the wearer – the second stop.

To precisely set the time of a wrist watch most movements are equipped with a second stop – when the crown is wound, the second hand doesn’t move. The seconds zeroing is a much rarer design.

When the crown is wound, the second hand continues to run until it reaches “60” and then it automatically stops – thus it is possible to use a time signal to set the watch to the second.

Model Overview Series 31


Modell 31.HS-12.1

fixed bezel

stainless steel polished, case sides in satin finish

Dial and Hands
deep black dial, hands made in steel

Special features
Nivarox hairspring, swan neck micrometer


Modell 31.HS-12.2

fixed bezel

stainless steel polished, case sides in satin finish

Dial and Hands
deep black dial, hands made in steel

Special features
Nivarox hairspring


Modell 31.HS-14.2

fixed sandblasted bezel

stainless steel bead-blasted

Dial and Hands
deep black dial, hands made in steel

Special features
Nivarox hairspring

Technical details


  • Calibre HS 81
  • Base: UNITAS 6497 Lépine. Modified as per a construction by Helmut Sinn
  • indirect center second
  • second stop at 60 when crown is pulled
  • 18 jewels
  • 18000 vibrations per hour; 2.5 Hz.
  • Movement diameter 16 1/2''' (36,6 mm)
  • Incabloc shock protection
  • Glucydur balance
  • Nivarox hairspring
  • Movement decorated with Geneva Stripes , blued screw hads, crown wheel and ratchet wheel with solar finish
  • Power reserve approx. 40 hours


  • Hours, minutes, indirect center second
  • Second stop at 60 when crown is pulled


  • Case made of stainless steel, polished
  • sapphire crystal glass, anti-reflective on the interior
  • screwed back with crystal glass
  • Pressure resistant up to 10 bar

Dimensions and Weight

  • Case diameter: 41.9 mm
  • Case thickness: 13.7 mm
  • Band lug width: 22 mm
  • Weight without strap: 71 Gramm

Straps 22 mm

Other Leather Straps

Leatherstrap Starfighter Pilot

Leatherstrap Starfighter Pilot

Black leatherstrap made of intensely grained cow hide with a subtle contrast stitching.

Vintage Black

Leather Strap Vintage Black

High-quality leather strap with black stitching, at the tip of the strap and at lug ends
Leather uppers, matte; Underside leather both cowhide. The thickness of the strap is approx. 3,3 mm.


Leather Strap Antique

Pull up leather with laquered edging and colored stitch, pin-clasp
folding-clasp available


Leather Strap Ozean

Black shark fish leather, pin-clasp


Leather Strap Arizona

Black Cowhide with alligator embossing, pin-clasp
folding-clasp available

Colour variants

light brown
dark blue


Leather Strap Montana

Armband Montana schwarz

Soft nappa leather in black, pin clasp
folding-clasp available

Colour variant

Armband Montana Hellbraun
light brown


Leather Strap Kroko

Leather Strap Kroko in black

Black alligator leather, pin-clasp

Colour variants

Leather Strap Kroko in dark brown
dark brown


Leather Strap Rustikal

Leather Strap Rustikal black

Black cowhide with alligator embossing, cushioned, contrasting seam white, pin-clasp

Colour variant

Leather Strap Rustikal mid-brown

Rubber Straps

Rubber Strap Kroko

Rubber Strap Kroko

Black rubber with alligator embossing, contrasting seam white, pin-clasp

Rubber Strap Glatt

Rubber Strap Glatt

Black rubber strap, smooth surface, incl. a laser engraved folding-clasp satinated or bead-blasted

Clasp overview

Pin Clasps

Stainless steel pin clasps

Pin Clasp polished
Pin Clasp satinated
Pin Clasp bead-blasted
Pin Clasp PVD coated

Folding Clasps

Folding clasps

Folding clasp, stainless steel polished
Folding clasp, stainless steel bead-blasted
Folding Clasp Rubber Strap bead-blasted
Folding Clasp Rubber Strap satinated