Reloj mecánico Otsuka Lotec n.º 5 Kai de hora saltante, de Jiro Katayama, arquitectura revisada, juego completo en estado casi nuevo

The No.5 改 is not simply a revision but a mechanical argument, refined and re-articulated. Where the No.6 leans toward retrograde poetry, the No.5 Kai behaves like a laboratory instrument: a jump hour and rotating minute track rise from layered machinery, and this near-mint example is a full set with a warranty dated 2025/12/18.

The Piece

Jiro Katayama's No.5 Kai, the revised architecture of the No.5, deliberately dismantles the traditional hierarchy of the dial. A central mechanical bridge sits over layered rotating discs, with peripheral minute indexing and a jumping hour display integrated into the mechanical depth. The layout reads like a pressure gauge, a mechanical counter or an industrial readout: time is no longer hands over a face but data emerging from machinery.

Some collectors pause at the Miyota base, yet Otsuka Lotec's work lies elsewhere. The modified base drives a re-engineered jumping hour system and a central disc architecture that exposes the choreography on the dial side, so the release of energy is visible rather than hidden and reading the time becomes an interaction rather than a glance. It is closer to mechanical interface design than to traditional horology.

The construction follows the same logic: matte steel surfaces, visible functional screws and emphasized structural geometry, with no decorative polish or Geneva striping. The 316L stainless steel case is finished in a blasted and brushed hybrid, and the sapphire crystal is set to give structural depth to the dial mechanics, placing the watch nearer to aerospace instrumentation and precision measuring devices than to conventional luxury.

Within Japanese independent watchmaking, where Kurono Tokyo stands for elegance and accessibility, Naoya Hida for classical purity and Hajime Asaoka for haute craftsmanship, Otsuka Lotec occupies its own category as the mechanical experimentalist: structural and conceptual rather than classical, decorative or nostalgic. Releases come in extremely limited batches, and the design is instantly recognizable.

Details

• Maker: Otsuka Lotec (Jiro Katayama)
• Model: No.5 改 (No.5 Kai, revised architecture)
• Origin: Tokyo, Japan
• Material: Industrial 316L stainless steel, matte blasted and brushed hybrid finish
• Movement: Modified Miyota base with proprietary jumping hour system
• Display: Jump hour and rotating minute track (central disc architecture)
• Crystal: Sapphire
• Strap: Black leather; original plus an additional strap
• Edition: Extremely limited batch release
• Included: Box, warranty certificate dated 2025/12/18, accessories complete

Condition

• Near mint, collector grade.
• Supplied as a full set with box, dated warranty certificate and complete accessories, including an additional strap.

Otsuka Lotec Atelier

Otsuka Lotec was founded in Tokyo by the designer and engineer Jiro Katayama, who came to watchmaking through industrial design, metalworking and a fascination with mechanical instruments rather than a Swiss apprenticeship. His founding idea was that a wristwatch could be treated as a miniature instrument whose architecture, materials and motion communicate time with the clarity of a scientific tool. Brushed plates, exposed screws, engraved scales, retrograde arcs and layered mechanical structures make the dial read like a laboratory gauge, an aviation instrument or a mechanical dashboard.

Models are identified by number rather than name; the No.5 Kai, No.6, No.7.5, No.8 and No.9 trace the evolution of Katayama's design language. Production is small-scale and atelier-like, often distributed in restricted quantities through lotteries or tightly controlled releases within Japan, and the watches typically combine reliable Japanese mechanical base movements with proprietary display modules of Katayama's design.

Authenticity & Care

Accompanied by the Otsuka Lotec warranty certificate dated 2025/12/18, original box and complete accessories. Every piece is examined and documented in Japan before dispatch and is offered with the Japonista authenticity guarantee.

Delivery from Japan

Packed by hand in Japan and shipped insured and tracked by EMS or an equivalent express service. Import duties and taxes, where applicable, are payable on arrival. Returns follow our published policy.

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