This week, independent Biel/Bienne-based manufacture Armin Strom debuted a new iteration of its Gravity Equal Force.

The Armin Strom Gravity Equal Force Ultimate Sapphire features a special gray-toned sapphire crystal off-center dial along with a black grain d’orge guilloche main plate, visible on the dial side of the watch — the latter of which was produced by hand at renowned Finnish watchmaker Kari Voutilainen’s workshop.

Armin Strom Gravity Equal Force Ultimate Sapphire

Armin Strom developed the first automatic watch with a constant force transmission — with the introduction of the Gravity Equal Force in 2019 — and this is perhaps the coolest version of the watch so far. Underneath the off-center sapphire crystal dial, which displays hours, minutes, and small seconds, the bridges and gears have been coated with a dark gray ruthenium treatment and given a circular-grained decoration. In contrast, the barrel and micro-rotor have been given a silver rhodium treatment. The 72-hour power reserve status is displayed on a small dial located directly on the mainspring barrel itself.

Armin Strom Gravity Equal Force Ultimate Sapphire dial close-up

The Armin Strom caliber ASB19 movement includes a stop-work mechanism that prevents the mainspring (using an Armin Strom developed “Geneva-drive equal force barrel”) from fully unwinding, which controls the power delivery (constant force).

Armin Strom Gravity Equal Force Ultimate Sapphire

Winding of the barrel is done by a micro-rotor, visible on the dial side. Running at 3.5Hz, the 25.52 mm x 11.67 mm, 28-jewel, 202 component movement can be adjusted by 4 regulating screws (free-sprung balance).

Armin Strom Gravity Equal Force Ultimate Sapphire caseback

Like the original design, the stainless steel case measures 41 mm x 12.65 mm, is 30 meters water-resistant, and the Lance-shaped hands have been finished by hand. The Armin Strom Gravity Equal Force Ultimate Sapphire comes with a black fabric strap with light gray stitching and a double folding clasp and will be available beginning in October, with quantities limited to 15 pieces for 2021, and up to 30 pieces in 2022. (Ref. ST21-GEF.SA.VE.M.30)

The retail price is $22,900.

Learn more at Armin Strom.

Posted by:Jason Pitsch

Jason Pitsch is the Founder of Professional Watches. He specializes in writing about and photographing timepieces.