NH34A

The NH34A is a mechanical watch movement developed by Seiko. Its complications include sweeping seconds, seconds hacking, a date display, a GMT hand, and automatic winding.

Here your see the watch hands (left), watch mechanism (top), watch stem & dial washer (top right), watch GMT hand (bottom), and dial (right).

Here is the reverse (watchmaker) side of the watch mechanism.

Here is the bottom of the dial. In the photo on the left, you can see that it has four dial feet. This is because this dial can work with NH style movements that have the winding stem at the 3 o’clock position, as well as ones with the 3.8 position stem. This does mean that one set of stems needed to be removed before installation. I did not get a photo of this while working on the NH36 movement, but that dial had the same feature.

Here is a photo of the dial washer, which is placed between the movement and the dial. It is slightly curved to add spring pressure to the mechanism and keep everything properly aligned.

The photo on the left shows the dial attached to the movement and the GMT hand installed. The GMT hand is the killer app of the NH34, a 24 hour hand that is set independently from the main timekeeping hands. This allows you to keep track of time in a different time zone (like Greenwich Mean Time, the Prime Meridian). On the right you can see the other three hands installed, though the hour hand is covered by the minutes hand and difficult to see.

Here you see the watch stem installed before and after trimming. Trimming the stem to the correct length for the case is important to allow proper function of the watch as well as waterproofing. The stem must be long enough for the crown to clear the the crown tube when pulled out to wind or set the watch, but short enough to allow the crown to screw fully into the tube. A gasket inside the crown as well as one on the crown tube create a water resistant seal once the crown is screwed down.

I added some grease to the stem to reduce wear and allow for smoother operation of the setting mechanism.

On the left you see a back view of the fully assembled watch, the glass back of the case showing off its internal components. On the right is the front view. Note that it takes some time for the date to properly roll over, so at ~11:45PM date is part way between the 4th and 5th. This is also a better view of the “Mercedes logo” style hour hand, which is an artifact of the application of the luminous material (lume) process. The lume is a liquid when applied to backs of the hands, filling the cutouts by way surface tension. To get a large area of lume, like the dot on the hours hand, supports need to be added.