Stefan Ketelaars Introduces the 3D Terra in Motion

With an inverted balance wheel.

Twenty-nine year-old Stefan Ketelaars started his eponymous brand in 2017, producing watches based on the ETA Unitas 6497 and 6498 but modified in a novel manner while still being affordable, starting at just €3,800, or about US$4,300. His signature complications are the “flying regulator” time display and spherical day and night display, but most notable is the balance wheel repositioned to the front of the watch.

The most recent model unveiled by Ketelaars Watches, the 3D Terra in Motion with Reverse Balance. The new watch builds on his earlier creation that features a miniature Earth that functions as a day and night display, but adds on the elevated balance wheel.

Like the rest of his watches, the 3D Terra in Motion is powered by a heavily modified Unitas 6497. But unlike the usual modified-Unitas fare in this price range that reshape the bridges for a new look, Mr Ketelaars retains most of the components on the back and instead reworks the front.

From the back, the distinctive Unitas bridges retain the same shape, but enhanced with pronounced, sloping bevelling on all the edges. The anglage is wide enough that its top edge almost touches the countersinks for the nearby screws and jewels.

A Ketelaars Unitas 6497 with a standard balance wheel on the back; the bridges are finished with radial graining and anglage

The Reverse Balance

The most significant modification on the new 3D Terra in Motion is the repositioning of the balance wheel. Instead of being on the back of the watch, it is elevated to sit on the dial. It’s essentially an inversion of the balance assembly that relocates it from one side of the base plate to the other.

The balance wheel and hairspring are secured by a U-shaped bridge at 11 o’clock, with the pallet lever bridge just below. From the back, the escapement is visible and located where it usually is.

While the reworked balance relies on a stock balance, hairspring, and regulator index, the balance bridge is made from scratch, as is the cock on the back that holds the escapement.

And the front of the watch also features a secondary gear train to drive the time display as well as the globe-shaped day and night indicator. The miniature Earth makes one rotation a day, and is in a fixed position relative to the hands.

Under all of that is a titanium dial that’s been hammered by hand to create a granular finish, while the hands are heat-blued titanium.

To accommodate the significant extra height of the movement, the crystal is a highly-domed, “box-type” sapphire, resulting in a watch that is thick – 13.5 mm high. And as with all Unitas-based watches, the case is a large 42 mm in diameter. It’s steel, simple in form and finish, and matched with an onion-shaped crown.

Note the high, domed crystal

Mr Ketelaars also offers various customisation options in terms of colours and finishing for the dial and movement. The bridges of the movement, for instance, can be finished with a radial or circular graining, or frosting. And they can be plated with nickel for a silver-toned finish, or etched with acid to create a darker grey.

The 3D Terra in Motion with a standard balance wheel (left), and the new version with an inverted balance

Key facts

Ketelaars Watches 3D Terra in Motion with Reverse Balance

Diameter: 42 mm
Height: 13.5 mm
Material: Steel
Water resistance: 30 m

Movement: Based on ETA Unitas 6497
Features: Hours, minutes, and spherical day-night display
Frequency: 21, 600 beats per hour (3 Hz)
Winding: Hand-wound
Power reserve: 46 hours

Strap: Various leather options with pin buckle

Availability: Direct from Ketelaars Watches
Price: From €5,800 before taxes

For more, visit


Back to top.

You may also enjoy these.