Otsuka Low-Tech, which won the Challenge Award at GPHG2024 and attracted attention, has announced a new product. Following on from the double retrograde and jumping hour models, they have now released the first satellite hour model in a Japanese-made watch.
The red arrow indicates the direction the disc will move. The first lottery sale will be held on March 1st from 6pm to 11pm on the official EC site (https://otsukalotec.base.shop/) Automatic movement (MIYOTA90S5 + in-house satellite hour module). 25 jewels + 2 ball bearings. 28,800 vph. Power reserve approximately 40 hours. Stainless steel case (40.5mm diameter). Water resistant for everyday use. 748,000 yen (tax included).
Text by Norio Takagi
Masatomo Yoshie: Photographer
Photographs by Masanori Yoshie
Edited by Yuto Hosoda (Chronos-Japan)
[Article published in the July 2025 issue of Kronos Japan]
The first satellite hour display in a Japanese-made watch, made possible by ultra-small bearings
The index of the cross-shaped numerals hanging from the tip of the three-pronged arm changes in sequence to indicate the hours, while at the same time acting as the minute hand itself - Otsuka Low-Tech, which has previously brought double retrograde and jumping hour watches to the world, and under the direction of Jiro Katayama, have taken on the challenge of creating Japan's first satellite hour time display mechanism. The name of the watch equipped with this mechanism is "No. 5 Kai." The case shape, with its volume on the upper and lower lugs, is clearly different from the existing "No. 6" and "No. 7.5," and is a continuation of the brand's first commercially available model, the No. 5, which was released in 2012. The No. 5 is a regulator watch with a disc display for the hours and minutes, and the name "Kai" embodies the idea that the satellite hour is an evolution of this.
The truly mechanical dial design is a true testament to Katayama's talent. And let's not forget the ease of use of the minute counter, which can be seen by peeking slightly at the dial from the cuff of a wrist. The satellite hour mechanism is driven by a reduction gear, visible below the 9 o'clock position. This gear is made extremely thin and has a two-layer structure with a spring between it, which automatically corrects the engagement with the drive wheel and eliminates the backlash that is inherent to satellite hour movements. This is a truly clever design.
The numerals are shifted by a ball bearing roller at the 8 o'clock position. MinebeaMitsumi was commissioned to provide a ball bearing with a large enough shaft to provide sufficient strength and that could be installed as close to the outer periphery of the dial as possible, and the company fulfilled the request beautifully. The disc-type small seconds also uses the company's world's smallest ball bearing. The No. 5 Kai model showcases Japan's outstanding industrial technology to the world.
