The Cheapest GMT Seiko Mod: Building an NH34 Watch on a Budget

GMT watches have always held a special place in the hearts of Seiko modders. If you’re a frequent traveler or your work requires you to collaborate with coworkers from a different timezone, a GMT watch is a very functional tool that takes just a glance to give you the time in different parts of the world. Most quality GMT watches come with hefty price tags though, with even entry-level options from established brands starting at around $500 to $1000.

Source: @beat_by_time on IG

But thanks to the release of the Seiko NH34, budget-conscious watch lovers and creative hands are now able to build their custom dual-timezone watch the way they like it, and without costing a pretty penny. An NH34 when paired with the right case, can create a flex-worthy watch that can stand up to pieces costing several times more. And on top of that, you can tweak it to match your personal tastes.

Why Build Instead of Buy?

Source: @watchlandph on IG

The question that often comes up is simple: why go through the trouble of building a GMT when you can just buy one? It’s a simple matter of economics and taste. Even the most affordable factory GMT watches, like Seiko's own 5 Sports GMT models, typically retail for $300 to $400. While that's certainly reasonable compared to luxury options, and while we’ll admit that the 5 Sports GMT line is already handsome as it is, building your own opens up a world of customization that simply isn't available with off-the-shelf pieces.

When you mod your own GMT, every component becomes a choice. The satisfaction of wearing something you've assembled with your own hands, tailored to your exact preferences, is something that can't be bought at any price point. It’s what Youtube Ashley Tee calls “the IKEA effect.”

More than just making a watch your own, the process is also a great way to learn. When you build a watch, you get to see how the movement works, how the case is put together, and how all the tiny parts fit and function as one. It’s a hobby that mixes a love for mechanics with the fun of working with your hands. Adding a GMT feature makes it even more interesting, since it brings in an extra challenge and makes the finished watch feel unique and rewarding.

The NH34 Movement: Your GMT Foundation

The movement is the most important part of any GMT watch mod, and the Seiko NH34 has quickly become the top choice for builders on a budget. This automatic movement is a caller GMT, which means the GMT hand can be set independently, while the main hour hand does not jump on its own. In practice, this makes it great for keeping track of “home” or reference time, though it isn’t as convenient for frequent travelers as a true flyer GMT. Still, it’s a genuine GMT complication and not just a simple dual-time display. 

The NH34 usually sells for about $90, which is very affordable compared to Swiss GMT movements that can cost hundreds or even thousands of dollars. But even at this lower price, it still carries Seiko’s strong reputation for reliability and accuracy. It comes with a 41-hour power reserve, runs at 21,600 vibrations per hour, and includes both hand-winding and hacking. What makes the NH34 especially attractive to modders is how well it works with existing Seiko cases and aftermarket parts. Its dimensions match popular case designs, and the stem height lines up perfectly with standard Seiko crowns and cases. That compatibility takes away most of the headaches that usually come with movement swaps, making the building process smoother and more beginner-friendly.

You just have to be mindful that dials for non-GMT movements like the NH35/36 need to have the center holes broached to accommodate the GMT post on the NH34, and that it’s advisable to always use a doubled domed crystal with it to make sure the hands don’t bump on the crystal.

Building Your Budget GMT: Recommended Cases

Let’s start off with the pricier cases that you can use to plan your GMT build around. These cases cost more than its peers because they are made specifically with the NH34 in mind but with strict tolerances for a premium feel.

NMK941 GMT Sub Case Mk 2

The NMK941 is perfect if you like the classic Submariner style (who doesn’t). It’s been updated to work with the NH34 movement and has a 1mm slimmer profile than the older version, while also being designed so you can use a flat crystal with it and still have enough headroom for the GMT hands. It also works with SKX007 bezels, bezel inserts, and crystals, so you can change up the look however you want. The case measures 40.5mm wide with 22mm lugs, which makes it a comfortable size for most wrists. 

NMK951 Alpine Tool Case

If you’d rather go for a rugged field watch vibe, the NMK951 is the way to go. Inspired by the Seiko Alpinist, it has a dual-crown design and an internal rotating compass bezel. At 39mm, it’s a little smaller and great for everyday wear. You can choose between a smooth bezel or a brushed GMT bezel, and there are nine different internal compass ring styles to mix and match with your dial. The case includes a flat sapphire crystal and sterile crowns for durability, and it’s water-resistant up to 100 meters. It’s also easier to mod with since the bezel and crystal are built as one piece.

NMK922 Dress/Tool Case

Lastly we have our NMK922 SRPE case, which is even smaller and sleeker with a 38mm diameter. This case only uses pilot bezels, so where do you put your 24hr scale to properly track the GMT function? One way is to use this Milspec dial which has a 12hr sector as well as a 24hr sector for your dual timezone needs. Alternatively, you can also use a GMT chapter ring if you prefer your dial a bit cleaner. Unlike the first two cases, this one does not have a bundled crystal - just remember to pick the doubled domed version for the hands clearance and you’re good to go.

Wrap Up

The combination of the NH34 movement and namokiMODS parts represents the sweet spot for budget GMT modding. The build process itself is rewarding too, teaching you valuable skills while creating something truly yours.

Ready to build your NH34 mod? Be sure to check out our huge catalog of Seiko mod parts; we have everything you might need, from the cases to the movements, down to the gaskets for water-resistance.

Happy modding!