Is Seiko MOD legal?

Q: I’ve been thinking about a topic lately and would love to hear your perspectives: How legal are Seiko MODs, and what exactly defines them?

From my understanding, “Seiko MOD” typically refers to modifying original Seiko watches—often by replacing parts like dials, hands, or bezels with aftermarket components. But I’m curious:

• Is it considered legal as long as original Seiko parts are used or the base watch is authentic?
• Does the term also extend to building entirely new watches using Seiko movements (like the NH series) and third-party cases/dials, and then selling them as “Seiko MODs”?
• How do these aftermarket parts compare to genuine Seiko components in terms of quality, design, and finishing? Are they identical replicas, or do modders often introduce custom designs?

I’ve seen some incredible creativity in the MOD community, but I’m also wondering where the line is drawn between modification, homage, and potential infringement.

Would appreciate any insights or experiences you’ve had with MOD builds, parts sourcing, or even legal considerations.

A1: This is an interesting question, because manufacturers and owners have completely different attitudes. At one end of the scale Seiko don't seem too worried about all the people who modifiy their watches and even supply movements to manufacturers who produce quite close homages. At the other end you have Rolex who if they find aftermarket parts on a watch at service time go nuts and who go after any company that dares to modify their watches just as hard as they would with illegal fakes.

My view is that if a watch is going to be sold as a Seiko, it needs to have all parts made by Seiko and correct for that watch. Any parts from a different Seiko model or aftermarket copies turn the watch into a franken watch at best, or a fake if an aftermaket dial has illegal Seiko branding.

The trouble with the Seiko modding scene is that although the original creator may be completely honest when selling, the subsequent owners may not. Any parts not made by Seiko will have unknown provenance and are unlikely to be as good as original parts.

A2: If it's your watch and your keeping it then do what you want and don't worry what others think. But as far as selling it then that's when you should be as honest as possible with what's been changed. That's the bit that causes a problem for others when people don't.

A3: I agree. I own a modded Rolex ref. 16710 GMT-Master II on which I have mounted aftermarket ceramic bezel inserts, an aftermarket sapphire exhibition caseback, and aftermarket oyster bracelet with a glide-lock clasp. All of these mods can be changed back to the original OEM configuration in a matter of a few minutes. In my opinion all have legitimate reasons; the bezel insert is more legible and not prone to dents, scratches, and fading like the original thin anodized aluminum inserts. The display caseback permits examination of the movement without removing the solid steel OEM caseback, and the glide-lock oyster bracelet is more substantial than the OEM bracelet and much easier to get finer adjustments as my wrist changes circumference with temperature.

None of these changes violate any Rolex trademarks, and I have never misrepresented the watch as all OEM. In fact, I am rather proud of the mods and discuss them freely when anyone asks about them. Not that I ever intend to sell it, but I would never sell the watch without returning it to OEM.

A4: I'd say it's the same as selling modified cars. Perfectly legal, and the original manufacturer has absolutely no say in it.

A5: I don't have a problem with modifying Seiko's, I wouldn't buy one, neither would I sell one. I see it as a good personal "teach yourself" tool, and if you make a pox of it then it hasn't cost you much, and you've learned something from your own folly, bear that in mind before you buy somebody else's botch up though, and a dressed up Seiko 5 is still a Seiko 5.

A6: "I wouldn't buy one, neither would I sell one," to quote my colleague is also my policy, and I wouldn't want to find that I had inadvertently bought a mod Seiko instead of a genuine one. I'm sure that if we entered deep into legal matters, we would find some restriction on mods, especially when it comes to selling numbers of these watches. However, actually taking someone to court for a breach of these restrictions would probably not be worth it and might be viewed as a joke. As for the vintage Russian-made Donald Duck watches, I can't see Disney taking action against them - fighting a legal case against the Soviet Union or even Putin's Russia was and is a non-starter.

A7: I'd say it's very much like cars. You can't buy a kit car and stick a Ferrari badge on it because they will chase you down. On the other hand say you wanted to make your Ferrari into a track racer you can pretty much change what you please and still call it a Ferrari and sell it on.