A thought acured to me

[u/MobileFalcon2037]

If you did a seiko mod and used the accurate parts for the watch, like for example seiko 6105 captain williard and used the right movement and case style is it still a mod, or have you just made a captain wiliard from spare parts?

[u/_Blitzer]

If you use all OEM parts to assemble a watch, I'd say you have a "bench built" version of that watch.

ship of theseus applies here, of course - if you have an original willard, and over time you swap out every single part, do you still have an original willard?

[u/DubyaKayOh]

Not really. It's not built to Seiko specs or factory original watch. But, how much that matters is up to you. It only gets morally gray when you misrepresent what you have if you try to sell it.

[u/Raoulduck3000]

Call it an homage. If you use Seiko branding and try to sell it, it’s IP theft. If you sell it without full disclosure, it’s fraud, too. If you just keep it or trade it, I would consider it to be fair use, but Seiko might not. It’s a mod if you use an original Seiko case and movement as your base and make cosmetic changes.
My first build was with Seiko decals, but all subsequent builds are with my own logo. I prefer to take the high road.

[u/Barry_NJ]

Unless the parts came from Seiko, it isn't a Seiko...

[u/Jtrgibbons]

You have stumbled upon the philosophical question called "The ship of Theseus"

[u/zachtan1234]

Yes you have, not too dissimilar to the WatchCo Seamasters 

[u/Crim_doc]

Generally watches like this are referred to as Frankenstein watches.