ETA 2639 is a robust automatic day-date workhorse from ETA’s 2600 family, widely used in reliable everyday watches from the 1970s onward. Below is a concise article with highlighted bullet points for quick reference.
Overview
The ETA 2639 is a Swiss-made automatic movement known for its practical day-date layout, central seconds, and durable construction suited to daily wear watches of its era. It belongs to the broader 26xx family, sharing many components and architecture traits with related calibers.
Key technical specifications
Automatic winding with central sweep seconds
Day and date display with quickset function
Diameter around 29.0 mm (13’’’ ligne size)
Height around 4.9–5.0 mm
Beat rate 21,600 vibrations per hour (3 Hz)
Power reserve typically around 40–42 hours
Jewel counts commonly 17, 21 or 25 jewels depending on execution
Design and construction
The architecture favors serviceability, with a conventional automatic module driving a centrally mounted seconds hand and a straightforward calendar mechanism. Bridges and plates typically follow the clean, functional finish expected from mid-range Swiss ébauches of the period rather than elaborate decoration.
Calendar and user features
Day and date arranged in a classic dual-window configuration on most dials using this caliber
Quickset calendar allows faster correction of at least the date, often both indications, via the crown
Hand-winding capability complements automatic winding for watches that are not worn daily
Practical watchmaking notes
Watchmakers often appreciate the ETA 2639 for its parts availability (shared with other 26xx calibers) and predictable behavior on the timing machine. Regulation to acceptable daily rates is usually straightforward, aided by the 3 Hz beat rate which balances shock resistance and energy consumption. For collectors and technicians, it represents a dependable, easily serviced vintage automatic movement rather than a high-complication or haute horlogerie piece.
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Stem, Crown, Hands & Spares might be available for this movement.
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