Brand History: From Restoration to Manufacture
Armin Strom was founded in 1967 in Burgdorf, Switzerland, by a watchmaker of the same name. The early business focused on restoration and skeletonization, which gave the brand a deep respect for hand finishing and movement architecture. In 2006, Serge Michel and Claude Greisler took over the company and moved it to Biel. They transformed Armin Strom into a modern manufacture with its own calibers, including resonance mechanisms and micro-rotor automatics.
The System 78 collection represents the brand's contemporary design language. The Gravity Equal Force is one of its most technically interesting models. It combines automatic winding with a constant-force mechanism, a rare pairing that addresses the problem of torque variation as a mainspring unwinds. The result is a watch that is both convenient and mechanically sophisticated.
The Movement: Caliber ARF19
At the heart of the Gravity Equal Force is the Caliber ARF19. It is an automatic movement with a micro-rotor, which allows the movement to remain relatively slim while offering the convenience of automatic winding. The micro-rotor is visible through the open dial, and its finishing is consistent with the rest of the movement: hand-polished bevels, circular graining, and polished screw heads.
The ARF19 runs at 25,200 vibrations per hour and delivers a power reserve of 72 hours. That is a practical figure for a daily wearer. The movement is not COSC-certified, but Armin Strom regulates its watches to chronometric standards. In real-world use, you can expect accuracy within a few seconds per day, though it will vary with position and temperature.
The most important feature is the patented equal-force mechanism. In a conventional automatic watch, the torque delivered by the mainspring decreases as it unwinds. That means the balance amplitude can drop, affecting accuracy. Armin Strom's system uses a stop-work declutch and an equal-force mechanism to deliver more consistent torque to the escapement. The result is more stable rate performance across the power reserve. It is a subtle technical achievement, but it is the kind of thing that matters to collectors who understand the difference between decoration and engineering.
The Equal-Force Mechanism Explained
To understand why the Gravity Equal Force matters, you need to understand the problem it solves. A mechanical watch is powered by a mainspring that unwinds gradually. When the spring is fully wound, it delivers more torque. As it unwinds, torque drops. This affects the balance wheel's amplitude, which in turn affects timekeeping. Many high-end watches use a constant-force mechanism to smooth out this delivery, but most are manual-wind or use a separate spring. Armin Strom's innovation is to integrate this with an automatic micro-rotor movement.
The stop-work declutch is a key part. When the mainspring reaches full wind, the automatic winding system disengages, preventing over-winding and reducing wear. The equal-force mechanism then takes the variable torque from the mainspring and releases it in a more consistent manner. The result is a watch that maintains its rate better as it runs down. It is not a tourbillon, and it is not a remontoir in the traditional sense, but it is a genuine solution to a real problem. For the collector, it adds a layer of mechanical interest that you can see and appreciate through the dial.
Dial and Case: Open Architecture
The dial of the Gravity Equal Force is not a traditional dial. It is an openworked display that reveals the movement's bridges, wheels, and micro-rotor. The hours and minutes are displayed in an off-center sub-dial at 12 o'clock. Small seconds run at 6 o'clock. A power reserve indicator sits at 9 o'clock. The layout is asymmetrical but balanced, and it gives the watch a technical, almost architectural feel.
The case is stainless steel, with a sapphire crystal on the front and a sapphire display back. The finishing is a mix of satin brushing and polished bevels. The lugs are sculpted and curve downward, which helps the watch sit comfortably on the wrist. There is no lume on the dial, so this is not a watch for reading in the dark. It is a watch for daylight and for close inspection.
The strap is black alligator leather, and it is secured with a pin buckle. The leather is supple and matches the formality of the watch. It is not a sports watch, and the strap reflects that. If you want to wear it casually, you might consider a custom strap in a more textured leather, but the original alligator is appropriate for its dressy character.
Legibility and Daily Readability
Despite the openworked dial, legibility is surprisingly good. The hour and minute hands are polished and stand out against the dark background. The small seconds is easy to read. The power reserve indicator is clear. The lack of a date means there is no visual clutter. In bright light, the sapphire crystal has anti-reflective coating, so reflections are controlled. In low light, you will struggle because there is no lume. But this is a watch for daytime and evening events, not for night missions.
Finishing and Architecture
Armin Strom's finishing is one of its strongest assets. The bridges are decorated with circular graining, and the bevels are hand-polished to a mirror shine. The screws are polished and blued in some areas. The micro-rotor is a particular highlight: it is openworked and finished on both sides, even though only one side is visible. This is the kind of detail that separates a true manufacture from an assembler.
The architecture is designed to be viewed. The open dial is not just a skeletonized exercise; it is a deliberate display of the movement's layout. You can see the gear train, the balance wheel, and the equal-force mechanism. The power reserve indicator is integrated into the movement, and it is legible without dominating the dial. The overall impression is one of depth and precision. It is not a flat, printed dial; it is a three-dimensional mechanical landscape.
Strap and Clasp
The black alligator strap is a classic choice. It is padded and stitched, and it tapers toward the pin buckle. The leather is soft from the start, so there is no break-in period. The pin buckle is made of stainless steel and is signed. It is simple and reliable. If you prefer a deployant clasp, you can order one from Armin Strom, but the pin buckle keeps the package lightweight and traditional. The strap is easily changed thanks to quick-release spring bars, which is a nice touch for a dress watch.
The System 78 Collection
The System 78 is Armin Strom's core collection. It includes the Gravity Equal Force, the Open Work, and the Tourbillon. Each model shares the same design language: open dials, visible movements, and a focus on mechanical architecture. The Gravity Equal Force is the entry point to the collection, but it is not an entry-level watch. It offers the same finishing and technical ambition as its siblings. If you like the Gravity Equal Force but want more complexity, the Tourbillon is the next step. If you want a simpler openworked design, the Open Work is worth considering.
Wearing Experience
On the wrist, the Gravity Equal Force feels substantial but not heavy. The stainless steel case has a solid presence, and the open dial makes it visually lighter than a solid dial would. The micro-rotor helps keep the profile manageable, so it slips under a cuff without much fuss. The lugs curve down, and the strap integrates well, so there is little dead space between the watch and the wrist.
The balance is good. The watch does not feel top-heavy, and the crown is easy to grip. The pin buckle is simple and secure, though some collectors prefer a deployant clasp for daily wear. The lack of lume means it is not a watch you will check in a dark cinema, but that is a trade-off for the clean, open dial. It is comfortable enough for all-day wear, and it has a wrist presence that invites conversation without being ostentatious.
Accuracy and Daily Use
Because the ARF19 is not COSC-certified, you should not expect a certificate. But Armin Strom is an independent manufacture, and its watches are regulated before delivery. In practice, you can expect accuracy in the range of -5 to +5 seconds per day, depending on how you wear it. The equal-force mechanism should help maintain that rate as the power reserve drops, which is a real advantage over conventional automatics.
The 72-hour power reserve means you can take it off on Friday evening and pick it up on Monday morning without resetting it. That is a practical luxury. The automatic winding is efficient, thanks to the micro-rotor, and the stop-work declutch prevents the mainspring from being over-wound. Day to day, it is a reliable companion for the office, dinner, and travel.
Comparisons and Alternatives
If you are considering the Gravity Equal Force, you are likely also looking at other independent watches. The Grönefeld One Hertz is a constant-force automatic with exceptional finishing, but it is more expensive and harder to find. The F.P. Journe Chronomètre à Résonance is a different kind of technical masterpiece, with two balances and a resonance system. The MB&F Legacy Machine Split Escapement is more sculptural and less traditional. The Romain Gauthier Logical One is another constant-force design, but it is manual-wind and has a different aesthetic.
Compared to mainstream luxury watches, the Gravity Equal Force offers something that a Patek Philippe Calatrava or a Vacheron Constantin Traditionnelle does not: visible mechanical innovation. Those watches are beautifully made, but they hide their movements behind solid dials. The Armin Strom invites you to look. It is a watch for someone who wants to engage with the mechanics, not just wear a symbol.
Occasions
This is a watch for formal occasions, daily office wear, and travel. It is dressy enough for a suit, but it has enough wrist presence for a casual dinner. It is not a sports watch, so you should not wear it for swimming or intense activity. It is not a travel watch in the sense of a GMT, but the 72-hour power reserve makes it a good companion for weekends away. It is a watch that transitions easily from boardroom to dinner.
Investment and Service
The Armin Strom System 78 Gravity Equal Force has a retail price of around $18,900. On the secondary market, examples typically trade in the $12,000 to $16,000 range, depending on condition and completeness. The trend is stable. This is not a watch that has shown the speculative spikes of some steel sports models, but it is also not a watch that has collapsed. It is an independent brand with a small production, and that tends to support values over time.
Service should be handled by Armin Strom or an authorized partner. The equal-force mechanism and micro-rotor are proprietary, and independent watchmakers may not have access to parts. Armin Strom does not publish a fixed service interval, but a mechanical watch of this complexity should be serviced every five to seven years, or when timekeeping becomes erratic. The cost will depend on the work required, but you should budget for a meaningful sum. This is not a watch you buy to save money on maintenance.
Who Should Buy It
This watch is for the collector who values independent watchmaking and mechanical substance. It is for someone who has already owned a Rolex, an Omega, or a Cartier and wants something that feels more personal. It is for someone who enjoys explaining what a micro-rotor is and why an equal-force mechanism matters. It is not for someone who wants a one-watch collection, because it lacks lume and a date, and it is not a sports watch. But as part of a collection, it is a standout.
It is also a good choice for the discerning buyer who wants to signal taste rather than wealth. The Armin Strom name is respected among connoisseurs, but it does not have the mass-market recognition of a Patek Philippe. That means it flies under the radar. For some, that is a drawback. For others, it is the whole point.
Pros and Cons
Pros: Patented equal-force mechanism; micro-rotor automatic; excellent hand finishing; openworked dial; 72-hour power reserve; limited production.
Cons: No lume; no date; not COSC-certified; limited service network; premium price; not a sports watch.
Final Verdict
The Armin Strom System 78 Gravity Equal Force ref. ST19-GEF.90.AL.M.35 is a connoisseur's watch. It pairs a genuinely innovative mechanism with beautiful finishing and a distinctive wrist presence. It is not for someone who wants a simple date window and a familiar logo. It is for someone who wants to look at their watch and see something new every time. If you value independent watchmaking and mechanical substance, this is a compelling choice.
