Is this 3135 movement legit?

As part of a job lot deal, a loose movement purporting to be a Rolex 3135 came into my possession a while back. Since it has had a top plate added which adds in a functioning day-date feature I had rather assumed it was a complete fake as I believe the genuine day-date models use the 3155. I have just looked closely and realised that I can't see any tell tale. It has a free sprung balance and Microstella adjustment and superficially at least looks like the real thing. Can anyone offer and opinion on its legitimacy? If its deffo fake I'll destroy it but if its a genuine 3135 with a mod it has some utility I guess once the bodged day plate is removed.

True. Some of the copies are no doubt plausible from a distance and junk when viewed up close. I’m banking on the fact the copies never have a proper working free sprung balance. At least I hope that’s so!

If you have plans for this movement, the hairspring will need professional adjusting. The overcoil is bent, and hairspring is off centre.

I’ve seen pictures of these fakes, before. And @padders is quite correct. The copies have a typical regulator, and are not freesprung like the watch in the picture, and the fakes don’t have the Mirostella weights on the rim of the balance wheel.

That’s interesting, thanks. If genuine then I might have had some use yes, but if it needs serious work as you suggest the I may be better off moving it on. I’ll get the top plate removed as that is at the least a non std mod. At worst fake.

Here’s the front. The mother of pearl dial is junk, chipped round the edge so whether it’s legit or not is a little moot. I assume someone bodged a 3135 into a day-date using a day plate of some kind, maybe in fact the module which Rolex themselves use to make the 3155. I was scratching my head about it trying to work out what I actually had but I think it makes sense now.