If Seiko’s 6139 movement can arguably claim the title for the world's first automatic chronograph in early 1969, its successor the oddly numbered 6138 - like this all original 1977 Japanese Domestic Market (JDM) SpeedTimer example here - can claim to be the most popular and versatile of the classic Seiko chronographs. The 6138 followed the 6139 closely with a 1970 debut, and like the 6139 was produced until 1979. Unlike the 6139, the 6138 had two subregister chronographs, with the addition of a 12 hour register. Seiko would release 10 different incarnations housing the revolutionary 6138 movement (a total of 18 variants) from 1971 until the end of production in 1979.
One of the most distinctive and popular executions of the 6138 was this all-original variant for sale here, the 6138-004X, or as it’s commonly known, the Seiko bullhead. Seiko’s bullhead was one of the most unusual chronographs Seiko made in the 1970s – a high order for a manufacture known for unique cases during this time period. In this execution, the movement was turned 90 degrees, with subdial placement at 9 and 3 o’clock positions, and the crown and pushers on top of the case. The bullhead, due to the large 6138, sits at 15mm thick on the wrist – not a thin movement – and although automatic, can also be hand wound.
The bullhead is one of the biggest and bulkiest vintage watches produced by Seiko during this era, and the large size of the Seiko bullhead contributes to its appeal and desirability - it was primarily marketed as a driver’s watch. That said, the orientation of the case has an ever so slight tilt at the 12 o’clock position to give it functionality when used in a motorsport setting.
The significance of the 6138 and 6139 movements to Seiko’s history cannot be emphasized enough, as both gave Seiko the honor of creating the world’s first automatic chronograph movement that featured a column wheel and a vertical coupling mechanism. Seiko successfully mass produced the layout for the column wheel and the vertical coupling mechanism, which was later adapted by Rolex for the development of the in-house movement used on the Daytona.
This 6138 comes with its original "fishbone" stainless-steel bracelet, NATO strap, Pelican travel case, and springbar tool.
1977 Seiko 6138-0040 JDM SpeedTimer "Bullhead" Chronograph Automatic
DIAL: Original reddish-brown dial, with clear hour indices. Day and date functions - with English and Kanji Japanese day variants - at the 6 o'clock position work correctly as designed. Hour and minute hands are subtely different in color, suggesting uneven wear or that one of the hands were replaced at some point in its nearly half century lifetime. Related, the SpeedTimer variant was unique through the three different 6138 bullhead examples, in that it didnt feature lumed hands.
CASE: Original hefty 44mm x 47.5mm stainless steel case. Matching original caseback. The bullhead's cushion-style stainless-steel case featured a polished upper-most portion, with the lower brushed; the brushed finish - albeit faint - remains on this example, thankfully, indicating - along with sharp caselines - this case has not seen a machine polish previous.
CRYSTAL: Hardlex crystal, with no deep scratches.
BEZEL: Original non-rotating bezel and insert inscribed with a tachymeter, a scale which drivers use to measure speed over a given distance. A single small ding in the bezel, below the tachymeter signature, typical for these watches given how high they sat on the wrist.
BAND: This bullhead comes with a Seiko-signed stainless-steel "fishbone" bracelet, which evinces normal wear - fits up to a 7.8 inch wrist. This 6138 also comes with a nylon NATO strap, with stainless-steel hardware - a comfortable compliment to this vintage bullhead.
MOVEMENT: Original 6138B Seiko 21-jewel automatic movement, manufactured in March 1977, which beats at 21,600 beats per hour.
CROWN: Original unsigned stainless steel crown.
CHRONOGRAPH PUSHERS: Pushers reset original main chronograph sweep and subdial hands to zero.