Ref. ST19-GEF.90

Gravity Equal Force Manufacture Edition Black

CHF 20'000

The Gravity Equal Force is the world’s first automatic watch with constant force transmission. The result is consistent power delivery to the balance which ensures that the watch always delivers flawlessly constant precision.


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Category: SKU: ST19-GEF.90


Stop-Work declutch mechanism and Equal Force Barrel

Stainless steel
Sapphire crystal and case back with anti-reflective treatment
Diameter: 41.00 mm
Height: 12.65 mm
Lug-to-Lug: 48.09 mm
Water-resistance: 30 m

Offset with subdial

Steel, manufactured by Armin Strom, decorated by hand

Delivered with a genuine alligator leather strap in black or blue
Width lugs/buckle: 20/18 mm

Pin buckle or folding clasp available in stainless steel



A key innovation, exclusive to the first set of System 78 watches, is the very first implementation of a “stop-work” declutch mechanism to be deployed in combination with an automatic movement. Typically seen only in haute-horology timepieces that are orders of magnitude more expensive, a “stop work” mechanism offers the benefit of more consistent energy transmission. To fully understand the benefit of this mechanism, one must first understand why an ordinary watch will not run at a consistent rate throughout the duration of its power reserve. The problem begins with the mainspring that inhabits every mechanical timepiece. A mainspring is a tightly coiled metal ribbon that resides inside of a watch’s barrel to deliver force to the movement. However, the force that a mainspring will deliver in an ordinary watch as it unwinds can never be delivered consistently, because the force provided will necessarily be higher when fully wound than it will be towards the end of its power reserve. To address this, Armin Strom implemented a “stop work” mechanism in the Gravity Equal Force that limits the mainspring from fully unwinding and thereby leverages only that part of the mainspring’s unwinding process which can deliver power most consistently.

The Gravity Equal Force’s Secret:
Always keep something in reserve.

As a demonstration of his commitment to the System 78 collection, co-founder and head-watchmaker Claude Greisler insisted on adding a stop-work declutch mechanism to an automatic winding movement for the very first time in horological history. The history of watchmaking has seen many solutions developed to address this problem, but none have ever been applied to a watch even remotely close in price to that of the Gravity Equal Force. In keeping with the mission of the System 78 collection to democratize access to haute horology timepieces, the extraordinary value proposition of this watch extends to the exceptional hand-finishing of its movement. The Gravity Equal Force fully embodies a core Armin Strom principle: to relentlessly innovate and thereby secure a new place in horological history with every timepiece that we develop, regardless of ultimate price point.

Visible micro-rotor and the newly-developed Equal Force Barrel

Even its barrel is innovative.

Building upon the classic stop-work mechanism architecture, Claude Greisler has developed an ingenious stop-work declutch system that operates inside the mainspring barrel to provide more consistent power delivery to the balance at every stage.

This Gravity Equal Force is a milestone timepiece. For the first time, a stop-work declutch mechanism has been combined with automatic winding in a watch movement to provide the best of both worlds.

Calibre ASB19

Automatic, 72-hours power reserve, off-centre time indications
Frequency: 25’200 A/h
Jewels: 28
Number of components: 202

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