Seiko 6660-7020 - A Rare Member of the Ultra-Thin Dress Series.
Between the late 1960s and early 1970s, Seiko's vision of haute horlogerie wasn't limited to Grand Seiko and King Seiko. During the same period, the brand also launched special-edition dress models distinguished by their ultra-thin casings, refined mechanical architecture, and hand-finished bezels. The Seiko 6660-7020 is one of the most distinguished references in this line—its lightness, thinness, and jewel-quality bezel make it a rare piece even today.
Fine Design and Craftsmanship: Multi-Faceted Bezel
One of the most distinctive features of this model is its bezel, featuring multi-faceted cuts. Each facet refracts light differently, creating a soft reflection that constantly changes as the watch moves on the wrist. This bezel type, used only on premium, thin-cased dress models in Seiko catalogs of the period, is:
The cutting process is entirely hand-cut (movements of the period could not automatically process this geometry),
Requires high precision,
Creates an elegant yet powerful optical effect,
Even today, it is considered extremely valuable by collectors because it is very difficult to restore.
This bezel is the strongest external evidence of the model's premium segment.
High-Class Mechanical Architecture in an Ultra-Thin Case
At just 8.4 mm thick, the 6660-7020 offers an exceptionally thin profile for its time, and the engineering behind it is also embedded within. The model features:
Seiko 66 Series - Gold-Plated Movement
The movement we see inside is the gold-plated version of the 66xx series. Gold-plated movements:
Increase friction and oxidation resistance,
Ensure long-term stability,
Preserve the aesthetic integrity of dress-segment models, and are only applied to select special editions.
The clean and shiny appearance of the coating is a strong indication that the movement has been used very little and has been perfectly preserved.
Technical Details:
21 Jewels - Diashock
Mechanical hand-wound construction
Precision-tuned balance bridge
Special low-profile architecture for a slim case fit
This movement embodies Seiko's "dress mechanical" philosophy: a caliber suitable for everyday wear yet technically robust.
Dial and Case: The Right Balance of Minimalist Elegance
Silver satin sunray-effect dial
Slim baton indices
Long baton hands preserved in their original form
Elegant lugs retain their sharp lines
Ultra-simple, completely clean design except for the logo
The model is devoid of any unnecessary details; the entire design is centered around highlighting the bezel's geometry and the movement's refinement.
Full Specifications
Reference: 6660-7020
Year of Manufacture: 1970
Thickness: 8.4 mm
Movement: Cal. 6600A (Gold-plated)
Operating Type: Manual-winding
Number of Jewels: 21 jewels
Frequency: 18,000 vph
Shock Resistance: Diashock
Bezel: Multi-faceted facet-cut
Dial: Silver satin sunburst
Glass: Acrylic
Cover: Snap-on
Strap: Black leather (unworn)
Collector Value - Why a Special Piece?
The features that make this reference valuable are as follows:
The faceted bezel is a product of special craftsmanship used in a small number of models of the period.
The gold-plated 66 series caliber inside distinguishes it from standard models.
Its proportions, thinness, and simple dial convey the character of a pure dress watch.
It's nearly impossible to find such a clean example.
It's one of the most refined members of its series, both technically and design-wise.
It's at the heart of what we might call Vintage Seiko's "most elegant face."
Condition
The watch is generally in very good condition. The bezel has largely retained its sharpness, the dial is clean, and the indices and hands are in their original form. The movement is exceptionally clean, and the gold-plated surfaces shine smoothly.
Conclusion
Representing Seiko's most refined approach to fine mechanical watchmaking, the 6660-7020 is a rare model that strikes a perfect balance between minimalism, craftsmanship, and technical elegance. The craftsmanship of the bezel, the premium nature of the gold-plated movement, and the ultra-thin case make this reference a true collector's item.
The item you're viewing was manufactured in 1970.
Professionally overhauled and FULLY SERVICED (the movement is completely disassembled, its components cleaned, oiled, and adjusted), your watch will function flawlessly without any surprises. (Maintenance-free for 3 years unless exposed to direct water or high humidity for extended periods.)
Item Condition: Tested, fully functional, and in working order.
