Vintage 1977 Seiko Black Bullhead 6138-0040 Chronograph

Vintage 1977 Seiko Black Bullhead 6138-0040 Chronograph

Nice Clean example from August 1977

I have just fitted a brand new aftermarket fishbone s/s bracelet as it had a horrible black strap.

Dial looks good, sub-register hands look to have been re-painted at some point in the past.

Im calling the outer bezel aftermarket as the dots above the numbers do not go to the edge.

Condition:

Used item, but it works properly with no issues.

Specifications:

Brand: Seiko

Model: Bullhead

Reference Number: 6138-0040

Movement: Automatic Chronograph, Seiko Cal. 6138

Case Material: Stainless Steel

Dial Color: Black / Steel Blue

Features: Chronograph, Day-Date, Tachymeter Bezel

Band: Stainless Steel Bracelet

Case Size: Approx. 44 mm

Lug Width: 20 mm

Max Wrist Size: Approx. 7.5inch

The Seiko 6138-0040, commonly known as the “Bullhead,” is one of Seiko’s most iconic vintage automatic chronographs from the 1970s. The nickname “Bullhead” comes from its unusual case design, with the crown and chronograph pushers positioned at the top of the case, giving the watch a shape that resembles the horns of a bull. It belongs to Seiko’s celebrated Speedtimer chronograph lineage, which followed the brand’s groundbreaking automatic chronograph development of the late 1960s.

This black 6138-0040 is especially admired for its bold and sporty appearance. It typically features a black dial with contrasting subdials and a black tachymeter bezel, giving it a sharper and more racing-inspired look compared with the brown/gold version. Collectors generally recognize two main 6138-0040 color variants: the brown/gold version and the black/blue version, with the black model offering a cooler and more technical 1970s chronograph style.

Inside, the watch uses Seiko’s 6138 automatic chronograph movement family. Seiko’s period datasheet for Caliber 6138A lists key specifications such as 21,600 vibrations per hour, automatic winding with auxiliary hand-winding, 30-minute and 12-hour chronograph registers, day-date calendar, quick-setting for day and date, and Diashock shock protection. Later Bullhead examples are also associated with the 6138B version, and collector references note that these are usually seen with 21 jewels, with rarer 23-jewel versions appearing in some Japanese-market watches.

Case measurements vary slightly depending on how they are taken, but dealer references generally place the watch at around 44 mm across the case, with a 20 mm lug width. This gives the Bullhead a large and very sporty wrist presence, even by modern standards.

As for production period, sources differ slightly, but most place the 6138-0040 in the mid-to-late 1970s, commonly around 1974 to 1978, while some references note that Bullhead variants continued to be sold until 1979.

Today, the Seiko Black Bullhead 6138-0040 is highly collectible because of its unusual case architecture, strong motorsport-inspired design, and importance in Seiko’s early automatic chronograph history. Collectors pay close attention to originality, especially the dial, bezel insert, hands, and movement, because many surviving examples have been refinished or fitted with replacement parts over the years.