It is not always immediately obvious why some of the complications that find their way onto the mechanical wristwatch might be viewed as particularly indispensable, but for the air traveller, international corporate executive, news, finance or communications personnel of the 1960’s, a watch with a 24 hour function must have carried a certain useful appeal.  Even now in the age of the smart phone, there is a certain something about the GMT/Navigator watch that pushes the right buttons. The earliest implementation of a 24 function in a Seiko wrist watch was the 6217-7000 World Timer which featured an inner rotating city bezel which allowed you to reference your current time zone with those in other parts of the world.

To be honest, I find those early 6217 World Timers somewhat aesthetically challenged, with the relatively compact dial sitting in the middle of a busy expanse of city bezel beneath a vast plexi-glass crystal. But the case does retain a certain early 60’s style in the detailing that I like, if not quite enough to feel any desire to acquire the complete package.

The second generation World Timer featured the 6117A movement, which is essentially a 6105A with the addition of a 24 hour wheel driven by the date driving wheel rather than a pinion mounted on the minute wheel in the 6217.  Seiko expanded the range to include Navigator timers that used a rotating 24 hour bezel in place of the city bezel, a somewhat simpler implementation but one requiring a little more knowledge of time zone differences.  By far the most desirable of these Navigator timers to my eyes is the 6117-8000 which features an external 24 hour bezel rather than internal.

The example that forms the basis of this latest entry I bought about two and a half years ago and it has since sat patiently waiting for me to get around to paying it some attention. In fact it’s been so long that somehow I seem to have acquired a second, that one missing its bezel but in the intervening period I’ve somewhat lost track of which one the bezel belonged to. It doesn’t much matter though as a few months after buying this one, I managed to find a new old stock bezel and so now I have a full complement of bezels to go with the two watches.

Our starting point then is the watch as received, complete with a rather weathered bezel, if possibly not the one originally fitted to this particular watch.

What strikes me immediately is that although this watch shows its age in the condition of the crystal and bezel, the hands and dial are close to immaculate. Looking to the rear reveals that it dates from May 1969

I always take it as a good sign when case backs are free from signs of watch case opener slippage, suggesting that if this has been serviced in the past, it was not performed by a complete klutz. That impression is reinforced once we gain access to the movement

While the rear of the case is certainly dirty, the movement looks very tidy indeed. A view of the dial unimpeded by the opaque crystal confirms its excellent condition:

There is even a suggestion of some life still in the 45 year old lume. The chapter ring lifts off the dial to reveal the dial spaced below:

With the dial off, we get a look at the one key difference between this movement and the 6105A used in the first generation 150m 6105 divers watch:

The 24 hour wheel sits atop of the regular hour wheel and is driven by the date driving wheel via the intermediate date wheel which sports an additional pinion on its upper side to mesh with the 24 hour wheel. As both the date driving wheel and 24 hour wheel rotate fully once per 24 hours, the logic of using the date wheel rather than the minute wheel to drive the GMT function seems obvious.

The one logistical issue deriving from the presence of the 24 hour wheel is one of clearance to the rear of the dial and for this reason the dial has a larger circular recess machined into its underside:

The movement’s a runner, although a touch ragged and losing about three minutes per day but it certainly looks in very decent cosmetic condition with the automatic mechanism removed:

The only minor fly in the ointment I discover when reassembling the movement after cleaning:

The pivot at the toothed end of the escape wheel is broken off. A replacement is easy enough to source from my parts bin and so the reassembly and oiling of the movement proceeded without further incident. Let’s pause a moment to take a look at the hour wheel, date driving wheel and intermediate wheel on the reassembled movement

before fitting the date dial, date dial guard and 24 hour wheel

The only remaining deviation from the routine is the fitting and alignment of the 24 hour hand, having first refitted the dial. This necessitated the purchase of a hand press with a large enough diameter to sit comfortably over the circumference of the 24 hour hand hole whilst having a large hole to clear the hour wheel tube.

Obviously it makes sense to fit the 24 hour hand at the point at which the date ticks over at midnight but then some care is required to make sure that the 24 hour hand is properly synchronized with the hour hand on its journey around the dial. There is a degree of play evident and my first attempt at aligning the hour and 24 hour hands at 16.00

resulted in the 24 hour hand lagging ever so slightly the following day as it passed the mid-day point. Removal and refitting seems to have sorted the problem but I’m not completely convinced that the alignment is perfect at every point on its 24 hour journey. I suspect some small degree of non-linearity in the gearing but I’ve got it more than well-enough aligned to satisfy the obsessive compulsive freak in me.

The rest is plain sailing. A clean case and fresh armoured acrylic crystal

the new bezel

some fresh gaskets for the crown and case back and in slips the serviced movement

for a quick spin before refitting the automatic winding mechanism

and we are home and dry.