Otsuka Lotec No. 7.5

Is a distinctive Japanese independent watch built around an unconventional jumping-hour display. Rather than using conventional central hands, the watch presents the hours, minutes and seconds through three separate display windows integrated into its architectural case.

The No. 7.5 combines Otsuka Lotec’s instrument-inspired design with an automatic Miyota movement and a proprietary jumping-hour module.

Otsuka Lotec No. 7.5

The No. 7.5 is immediately recognizable by its turret-like three-window architecture. Each opening performs a different function: the jumping-hour display indicates the hour, while separate discs display the minutes and seconds.

The case measures 40mm in diameter and combines straight hairline finishing with sandblasted surfaces. This mixture of textures emphasizes the unusual geometry of the watch while giving the stainless-steel case a technical, instrument-like character.

The newer specification introduced from 2023 uses 316L stainless steel and upgraded sapphire components for improved durability.

Jumping Hour Display

The defining feature of the Otsuka Lotec No. 7.5 is its jumping-hour mechanism.

The hour changes instantaneously through the dedicated jumping-hour display, while the minutes and seconds are shown on separate discs. This creates a mechanical display system that differs substantially from traditional watch layouts.

The three apertures are positioned across the top of the case and use sapphire crystal components. The hour display incorporates a custom sapphire fisheye lens designed to enlarge the indication beneath it.

Miyota 82S5 Automatic Movement

The No. 7.5 is powered by a Miyota 82S5 automatic movement combined with Otsuka Lotec’s in-house jumping-hour module.

The movement and module assembly contains 24 jewels and operates at 21,600 vibrations per hour, or 3 Hz. It provides approximately 40 hours of power reserve.

The movement is visible through the exhibition caseback, allowing the mechanical system to be viewed from the reverse side of the watch.

40mm 316L Stainless-Steel Case

The newer No. 7.5 specification uses 316L stainless steel and measures 40mm in diameter.

The case is finished using both hairline brushing and sandblasting. The combination creates contrast across the case surfaces and reinforces the industrial character of the design.

The case measures approximately 11.2mm thick, with a maximum thickness of approximately 14.8mm around the raised display structures.

Sapphire Crystal and Fisheye Lens

The current No. 7.5 specification uses sapphire crystal with anti-reflective and anti-fingerprint coatings.

The individual display architecture includes a custom sapphire fisheye lens for the hour indication. This is one of the significant technical changes introduced with the updated model from 2023.

Japanese Independent Watchmaking

Ōtsuka Lōtec is a Japanese independent watchmaker known for unconventional mechanical displays inspired by instruments and machinery.

The No. 7.5 reflects that approach by treating the watch dial more like an information panel than a traditional watch face. The jumping hour, minute disc and seconds disc each occupy their own dedicated opening.

The model is produced in Japan and has attracted attention among collectors interested in independent Japanese horology and unusual mechanical time displays.