Guide 03
What is a Seiko mod?
A term you'll see everywhere once you start looking at custom watches. Here's what it actually means, and what it doesn't.
The plain definition
A "Seiko mod" — short for Seiko modification — is a watch built or customised using parts compatible with a handful of widely used Seiko movement and case architectures. Because those architectures are reliable, affordable and easy to source parts for, a whole ecosystem of interchangeable dials, hands, cases and bezels has grown around them, shared between small brands and hobbyist builders.
What it isn't
"Seiko-compatible" describes parts and case architecture compatibility. It does not mean an official Seiko product, licence, partnership or endorsement.
Eximius Watches is an independent brand. We are not affiliated with, endorsed by, or authorised by Seiko, and we won't imply otherwise.
How we approach it
We don't sell loose parts, and we don't do one-off mods to order. We choose and combine the case, dial, hands and bracelet ourselves, then assemble them by hand for each order — using Seiko-compatible components as part of the supply chain for some builds.
So it's one category within a broader custom mechanical watch brand, not the whole identity. Longer term, the direction is toward our own branded dials.
Done for you, or do it yourself
Sourcing
- Eximius
- We source the components and check they work together.
- DIY modding
- You find the parts and take the compatibility risk.
Assembly
- Eximius
- Assembled and regulated by hand, then inspected.
- DIY modding
- Your bench, your tools, your patience.
If something's wrong
- Eximius
- Two-year warranty and support you can email.
- DIY modding
- No warranty if a part doesn't fit or doesn't run.
| Eximius | DIY modding | |
|---|---|---|
| Sourcing | We source the components and check they work together. | You find the parts and take the compatibility risk. |
| Assembly | Assembled and regulated by hand, then inspected. | Your bench, your tools, your patience. |
| If something's wrong | Two-year warranty and support you can email. | No warranty if a part doesn't fit or doesn't run. |
Related terms
The vocabulary you'll meet in Build Your Watch:
Movement
The mechanical engine inside the watch. Everything else is built around it.
Automatic
Self-winding from the motion of your wrist. No battery.
Case & dial
The body of the watch, and the face you read. Two of the four things you choose.
Hands & bracelet
What points at the time, and what holds it on your wrist. The other two choices.
Where to go next
If you want the technical detail, read NH35 vs 8285. If you'd rather just start choosing, the builder walks you through it four steps at a time.