While the story of the Suwa Seikosha produced Astron 35SQ is well known in esoteric watch circles, what isn’t well known was Daini Seikosha was developing its own quartz calibre at the same time, the 36SQ, which was released in 1970 - like this 36SQ-derived Deep Blue gradient-dialed 1973 Seiko 3923-5010 watch here, on a near new-old stock (NOS) vintage Seiko-signed stainless-steel bracelet.
 
But first some history - 1969 was one of the most spectacular in Seiko’s storied history.  That year, it released the world’s first automatic chronograph, the Calibre 6139 and the V.F.A. (Very Fine Adjusted) movement – which delivered Seiko’s highest yet level of precision for a mechanical movement.
 
Seiko would release another first upon the world, the first quartz wristwatch - the Seiko Quartz Astron, which went on to change the way the world told time, and severely tested the dominance of the Swiss, bringing high technology within the reach of all.
 
Despite several watch manufacturers had been developing quartz calibres throughout the 1960’s, Seiko was the first to market with the Astron 35SQ in December 1969.  Despite costing ¥450,000, the same price as a small family car, they still found buyers (100 in the first month) and the model signaled the start of the quartz revolution.
 
The 36SQ doubled the internal clock speed of the 35SQ (from 8192Hz to 16384Hz) while providing an increased accuracy of 0.1s/day (3s/month), and claimed to better the 35SQ in all aspects.  Despite featuring in Seiko catalogues, it’s not immediately clear the 36SQ was ever commercially released - no examples have been found in the wild, though there is an example displayed in the Seiko Museum in Tokyo.
 
Regardless, following the release of the Astron, Daini continued to improve the 36SQ, producing two calibres, the 3922A and the 3923A (like the one on offer here), with the only difference between the two being the inclusion of a day display for the 3923A.
 
Rather atypical about the case on this 3923?  The faceted crystal is wedge shaped in profile with beveled edges and has the white “Quartz” moniker, transfer-printed on the underside.  The 3923 case is a mix of polished, brushed, curved and angular surfaces (a little akin to Grand Seiko’s “Grammar of Design”), with a curved caseback to follow the shape of the wrist.
 
Produced for just four years, from 1972 through 1976, Seiko’s 39xx series calibres were the flagship of Daini’s quartz production.  Hand soldered and adjusted to six positions and temperature, they were accurate to +/-10 seconds per month, hence the ‘Very Fine Adjustment’ (V.F.A.) branding on the dial.  By today’s standards this may not sound very accurate, in 1972, 0.3 seconds/day was excellent timekeeping for a quartz calibre.
 
Another highly unique aspect of this 3923 is of course the LED which is located in the top right corner of the dial.  The LED filament is mounted inside a plastic ring on the calendar side of the movement and the dial is fitted with a faceted jewel which covers the LED housing and projects its light in all directions.
 
The LED flashes once every second with the purpose of providing an indication of the level of battery power.  When the batteries are new, the light is bright and it fades gradually until the light extinguishes completely, at which point thew wearer knows a battery change is imminent.  
 
This Seiko V.F.A. 3923 comes on an original Seiko stainless-steel bracelet, and with leather strap, rugged travel case, and springbar tool.