Most people notice the dial first.
The color, the bezel, the bracelet, the way the watch catches light — those are usually the details that draw attention immediately. But for watch enthusiasts, the real heart of the watch lives underneath the dial.
The movement.
The movement is what powers the watch, controls its functions, and ultimately defines how the watch feels on the wrist. Maybe it's a clean GMT, a gorgeous skeletonized dial, or a chronograph that looks straight out of a racing pit. You're drawn to the design, the price, the whole vibe. But here's the thing a lot of people overlook: what's actually ticking inside that watch matters just as much as how it looks on your wrist.
Let's break down every major movement you'll find in a Seiko mod, what makes each one special, and which one might be right for you.
NH35 — The Starter
If there's a "heart of the Seiko mod world," it's the NH35. This movement shows up in more mods than any other, and honestly? It's earned that spot.
An automatic movement means the watch is powered by motion rather than a battery. So when you see an NH35 in your mod, you're not getting some cheap knockoff. As you wear the watch throughout the day, a rotor inside spins naturally and stores energy inside the mainspring.
What makes it great:
- Automatic & hand-winding (you can also wind it manually by the crown — super useful after it's been sitting in a drawer)
- Hacking seconds — the second hand stops when you pull the crown, so you can set the time with precision
- Date display at 3 o'clock
- 24 jewels
- 41-hour power reserve
- Accuracy of roughly ±20–40 seconds per day
That is why the NH35 became the foundation for so many Seiko mods, especially:
- Dive watches
- Datejust-style builds
Find more Datejust watches: Datejust collection Watches By Cody
NH34 — The Rise of the GMT
As GMT watches became more popular, the NH34 quickly became one of the most important movements in modern Seiko modding.
The NH34 is essentially a GMT version of the NH35. It keeps the same dependable automatic platform while adding an extra GMT hand that allows the wearer to track a second time zone.
Originally, GMT watches were designed for pilots and travelers. Today, they became one of the most recognizable styles in watch culture because they feel sporty, technical, and adventurous.
What to know:
- Same base architecture as the NH35 (24 jewels, 41-hour power reserve, hacking, hand-winding)
- Independent GMT hand that rotates over 24 hours
- It's technically a "caller GMT" — meaning the GMT hand and main hour hand adjust together, not independently like a true GMT. For most people, this is completely fine.
Find more GMT Watch at: Watches By Cody GMT Collection
NH38 — Mechanical Beauty on Display
Some watches are designed around simplicity.
Others are designed to showcase mechanics.
That is where the NH38 comes in.
The NH38 is commonly used for open-heart designs, where part of the movement becomes visible directly on the dial. Unlike the NH35, which includes a traditional date wheel, the NH38 focuses more on visual presentation and mechanical character.
Open-heart watches create a completely different emotional experience. Instead of hiding the mechanics underneath the dial, the movement becomes part of the design itself.
It makes the watch feel more alive, more technical, and more interactive on the wrist. For many collectors, the appeal of mechanical watches comes from being able to appreciate the engineering behind them — and the NH38 helps showcase that beautifully. What you do get is a beautifully balanced dial with a subtle open-heart aperture at 9 o'clock, where the balance wheel and escapement peek through. It's understated. It's elegant. It's the move if you care about visual symmetry.
Find more Nautilus watches at: Nautilus Collection Watches By Cody
NH70 & NH72 — The Skeleton Specialists
If the NH38 introduces open-heart design, the NH70 and NH72 take things even further.
These movements are fully skeletonized, meaning much more of the internal mechanics are exposed across the dial. Instead of seeing only a small section of the movement, you can see gears, bridges, and moving mechanical components throughout the watch face.
Skeleton watches feel architectural.
They turn the movement into the centerpiece of the design.
This style became especially popular in luxury-inspired integrated bracelet watches because the exposed mechanics create a futuristic and highly technical appearance.
The NH70 and NH72 are often used in:
- Santos-inspired skeleton builds
- Avant-garde designs
- Modern luxury Seiko mods
- Statement pieces
Find more Skeleton watches : Santos Skeleton Watches By Cody
VK63 — The Chronograph Favorite
The VK63 is slightly different from the other movements because it is not fully automatic.
Instead, it is what enthusiasts call a “mecha-quartz” movement.
That means the watch uses quartz timekeeping for accuracy while still delivering a mechanical-style chronograph experience. The pushers feel crisp and tactile, and the chronograph hand resets with a satisfying snap similar to more expensive mechanical chronographs.
This combination made the VK63 incredibly popular.
Why not just use a mechanical chronograph? Because a reliable automatic chronograph at this price range would either be too thick for the cases or too unreliable over time. The VK63 is simply the smartest technical choice for mods with a chronograph complication.
- Daytona-inspired builds
- racing chronographs
Find more Daytona watches at: Daytona collection Watches By Cody
Choosing the right watch is ultimately about more than just specifications—it’s about finding a piece that fits seamlessly into your daily life. The best watches are the ones you don’t have to think twice about—reliable, versatile, and naturally aligned with your personal style.
At Watches By Cody, our goal is simple: to offer watches that combine timeless design, dependable performance, and real-world wearability—without the unnecessary markup often found in traditional luxury retail. We focus on pieces that look refined, feel right on the wrist, and hold up over time.
If you’re ready to find a watch that fits both your style and your lifestyle, explore our latest collection at Watches By Cody and discover the piece that works for you.
