One of the worlds oldest automatic chronographs turns 50!

Seiko 6139 ProjectI picked this Seiko 6139-6010 up from Japan. The Serial number shows it was made in March 1969 and that means this month it turned 50 years old. The earliest I have seen are from February 69. It’s one of my favourite dial and case designs; 6139-8010 AD starburst blue with frost and red hands. This example is in very good original condition. It’s not running and I suspect it once received a good knock as the central second recorder has fallen off and the upper shock jewel is missing.

The first letter in the Serial number tells you what year it was made. (You guess the decade) and the second number tells you what month.


The shock jewel and spring is missing. Otherwise the movement looks very good.


I have removed the osculating weight.


The Tachometer ring is held in place by the dial and has a notch to hold it in the correct position.


The dial is in excellent condition. If you look at the 2’o clock indication, you can see where the Tachometer ring is held in place from.


The date disk is held in place with a clip.


Here you can see the day/day mechanism.


I now start taking apart the movement.


The chronograph runner has a vertical clutch mechanism.


Movement almost taken apart.


Movement has been cleaned and is ready to be put back together.


The mainspring is oiled and put back into the barrel.


I have found and fitted a new upper shock jewel and spring. Here I see that the balance moves freely.


Movement coming together. It can be a little fiddly fitting the wire springs, but practise makes master;)


Movement almost back together.


I fit the balance and it starts ticking straight away.


For being an old Seiko 5 that looks great.


Setting/date and day mechanism back in place.


Setting the movement can be a little tricky due to the special second hand axle.

Speedtimer 5 Sport 70 meter proof 6139 Seiko 6139A service For now this one is a keeper.   Seiko 6139 8000 Yep holding on to this one! Unless I get an offer I can’t refuse;)   This watch also has quick set day date function! That would also be a first in a auto chronograph.

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