URWERK makes about 150 watches a year. The UR-101 Green Mamba, unveiled in Geneva today, is a 50-piece edition, a third of that, and it is a homecoming. The UR-101 was one of the first watches the brand ever showed, at Baselworld in 1997. Nearly 30 years on, URWERK has stripped it down to two colors: a black case that soaks up light and an emerald display that seems to float out of it.

What is the URWERK UR-101?
Most watches use hands. The URWERK UR-101 uses what the brand calls wandering hours. Inside, a carrousel carries the hour numerals on two satellites. The current hour drifts along a 180 degree arc marked with the minutes, and where the numeral sits on that arc tells you the minutes. When it reaches the end, the next hour has already rolled in at the start. It reads like a gauge on an instrument panel more than a clock face, and it is what URWERK means when it talks about radical legibility.
The name is part of the story. URWERK points back to Ur of the Chaldees, the Mesopotamian city whose people tracked time by the shadows the sun cast on their monuments, and to the German word werk, for work and creation. The brand was founded in 1997 by master watchmaker Felix Baumgartner and artist Martin Frei, and the UR-101 is where its idea of time as a path, rather than a circle, began.
UR-101 Green Mamba: why black and green
Frei, who sets the look of every URWERK model, explains the color in the official press kit. He wanted an object that becomes almost invisible, then reveals itself a moment later, in a techno green he compares to the control panels of a spaceship and the glowing eyes of a mamba in the jungle. The case is coated in what URWERK calls Panter Black, a nod to the Millennium Falcon from Star Wars. Baumgartner puts it more simply: black lets the watch disappear, and green gives it an identity.
There is a second reference hiding in there. Frei says the arc display takes the watch back to the Renaissance, when astronomical instruments gave watchmaking a new way of telling time.

UR-101 Green Mamba specs
- Case: black PVD-coated steel, 41 mm wide and 10.3 mm thick, with a glare-proofed metallised sapphire crystal.
- Movement: self-winding Calibre UR-1.01V, 28 jewels, 4 Hz, 48 hours of power reserve, finished with snailing, sandblasting and satin-brushing.
- Display: wandering hours on two satellites plus minutes, with Super-LumiNova on the markers.
- Strap: black rubber lined with black calfskin, on a black DLC pin buckle.
- Water resistance: pressure-tested to 30 m, so a desk and dinner watch, not a swim watch.
- Edition: 50 pieces.

How it fits the UR-101 family
The Green Mamba joins two other current UR-101 versions: the T-Rex in a guilloché bronze case and the Diamond Sky, set with 214 diamonds. The Green Mamba is the quietest of the three until you look at the dial, and it is the one that comes closest to the 1997 idea of reading time and nothing else.
If you like watches that tell time a different way, see the Bell and Ross BR-03 Space Mission with its moon and spaceplane, or the Depancel watch built to count a 24 hour race.
Where to buy the UR-101 Green Mamba
- URWERK UR-101 Green Mamba. The 50-piece edition is sold through URWERK's network. Find an authorized URWERK retailer.
- URWERK UR-101 T-Rex. The textured bronze version of the same design, if you would rather wear the color on the case than the dial. See the UR-101 range at URWERK.
More on the founders is on URWERK's own story page.
Our call: buy, if you can get an allocation. This is URWERK's founding idea in its most graphic form, and at 41 mm with a rubber strap it is one of the most wearable things the brand makes. Fifty pieces from a brand that makes about 150 watches a year means more requests than watches, so if you want one, ask a retailer now rather than wait for reviews. Just know what you are buying: a design object with a 30 m rating, not a tool watch.