I’ve featured these JDM 6306-7001 divers before but this one is in such exceptional condition I’d be doing the Seiko enthusiasts that read my blog a disservice if I didn’t show it! It arrived from a prominent Seiko collector based in the far east for a service and re-seal, it always astounds me how examples like this can survive so well. I’ll be featuring a few more of this chaps collection as they get on the bench as he has some truly jaw dropping pieces. Here it is as it arrived, the dial plots have turned a lovely creamy colour.

The caseback shows it was manufactured in August 1976 which is a very early example of this model, this is reinforced by the large splines on the crown, the splines became finer later on in production. Also note the frosted background to the tsunami logo, you usually see this background detail polished smooth through wear.

The first look inside shows a super clean movement that just needs all the old lubricants cleaning and and fresh oils re-applied. It may not sound like much to be done but the amplitude on this was way down when checked on the timing machine, it should make a huge difference when it’s serviced.

Look at that dial and handset, in absolutely beautiful condition.

No problems underneath the dial as to be expected, all’s in lovely condition. The kanji day ring option is present as this is a JDM model.

With the movement turned over I can start on the motion work side.

Nothing but super clean undamaged parts!

The movement was soon in it’s constituent parts ready for cleaning and inspection.

Once the parts had been on a trip through my vintage 1974 Vari-Matic  I inspected them, nothing untoward was found as you’d expect. The rebuild started in my usual way….

The train is ready for the bridge in this shot.

The bridge and pallet fork refitted here.

The balance and ratchet wheel back in place in this photo, this allows me to wind the mainspring and get it on the timing machine to do the primary adjustments, with the clean jewels and pivots the amplitude was back to normal.

Once the primary adjustments were done the auto work can be refitted.

The movement was flipped over and the calendar side was re-assembled.

Then the dial and hands were refitted.

One of the beauties of the 6306 and 6309 divers is that as long as the case components and seals are in good condition they can be made water resistant once more. The usual failure point is the crown seal, here you can see where the original seal has started to break up and deposit shards of rubber on the stem.

To replace the seal the stem has to be removed.

This gives access to be able to remove the old seal, if you look inside the crown below the threaded portion and washer you can see the wear on it.

Once it’s out and next to a new one you can see the difference.

The assembled crown ready for refitting.

The case was stripped for an ultrasonic clean, this also allows the underside of the crystal to be fully cleaned.

Here the movement has been recased, there’s also a fresh case seal ready for the caseback to be fitted.

Now it’s time for a leak test….

….which it passed of course. The watch was now complete, just a period of testing to undergo and it can be sent back, what a corker!