MITKA

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.
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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.

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

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I have removed the osculating weight.

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

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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.

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The date disk is held in place with a clip.

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Here you can see the day/day mechanism.

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I now start taking apart the movement.

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The chronograph runner has a vertical clutch mechanism.

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Movement almost taken apart.

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

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The mainspring is oiled and put back into the barrel.

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

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

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Movement almost back together.

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I fit the balance and it starts ticking straight away.

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For being an old Seiko 5 that looks great.

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Setting/date and day mechanism back in place.

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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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