Otsuka Lōtec No. 7.5 — Jumping Hour | Jiro Katayama

Otsuka Lōtec No. 7.5 — Jumping Hour

Maker: Jiro Katayama  ·  Origin: Tokyo, Japan  ·  Full Set

Jiro Katayama is a self-taught Tokyo artisan who founded Otsuka Lōtec to celebrate raw, “low-tech” mechanics. Operating out of the Otsuka neighbourhood, he uses manual machinery to craft fewer than 200 pieces annually. In 2022, he partnered with AHCI master Hajime Asaoka to refine his production architecture.

The No. 7.5 is his terminal expression: a dial stripped of traditional hands, replaced by three magnified “fisheye” sapphire lenses. It functions like an analog gauge, featuring a proprietary jumping-hour module that snaps forward with a tactile click. A mechanical instrument for the wrist — rare, lottery-only, and deeply Japanese.

Key Features

• Complication: Proprietary jumping-hour module with tactile click
• Display: Three magnified fisheye sapphire lenses — no traditional hands
• Production: Fewer than 200 pieces annually — lottery allocation only
• Maker: Jiro Katayama — self-taught Tokyo artisan, AHCI-adjacent
• Collaboration: Production architecture refined with AHCI master Hajime Asaoka (2022)
• Condition: Full set