The Seiko Chronograph automatic 6138-0040 (Bullhead) was introduced in 1969, mass production began in late 1970 and lasted until 1979.
6138 movement equipped with a manual wind, it is built into a every Seiko two sub dials chronograph, the only difference in Bullhead is in the day/date discs because the Bullhead has a day/date display at number six. There were 2 versions of the 6138 movement: 6138A with 21 jewels and 6138B with 23 jewels.
It was also produced in two variants, black and brown dial. It is interesting to note that the Bullhead design was created in order to chronograph pushers moved from the standard position towards the top of the watch to prevent their unintentional activation. The Bullhead is one of the biggest and thickest watch that Seiko ever produced. It measures 44mm in diameter and thickness is 15mm. It have hi-quality build all stainless steel case and hardlex crystal, fishbone bracelet is made of solid steel links, and it is specially made for this model because it is asymmetrical more precisely, the width of the ends that go up to watch is different. Bullhead must be on the original bracelet to be complete.
It’s enjoyable to have and wear these watches, so get your while they can still be found. This is the 70s cult Seiko watch.