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Have even seen it suggested that some Sellitas actually are ETA kits, merely assembled by Sellita.
Selita literally made movements for ETA for decades, they are part of ETA's heritage.
You do read about the rotor bearings being noisier and/or less reliable on the Sellita autos, and that's one part that does look visibly different from what I've seen. I'm no expert or watchmaker though, obvs.
This is possibly true, I have a couple of noiser Selita movements but they are just base movements with no improvements. ETA movements aren't the quietest in their base form either. When I learned to service the 2824, I was really suprised at how "unfinished" the movements was side by side with a manufacturer modified one. It takes a lot of work to get an ETA movement to look good enough to have a display back case, and a mountain of work to add common enhancements.
In any case, fuck it, Eterna invented the bearing rotor and do it better than anybody imho and they use Selita as a base movement if my memory serves me correctly.
Stonehedge-
There are several different grades of each ETA movement. For the 2824 there are four grades:
STANDARD GRADE: This grade is adjusted in two positions, specified with an average rate of +/-12 seconds per day, with a maximum daily variation of +/-30 seconds.
ELABORATED GRADE: This grade is adjusted in three positions, specified with an average of +/-7 seconds per day, with maximum daily variation of +/-20 seconds.
TOP GRADE: This grade can be adjusted in 5 positions, specified with an average rate of +/-4 seconds per day, with a maximum daily variation of +/-15 seconds.
CHRONOMETER: This grade, unlike the others, is always serial-numbered
as a result of the requirement of the certification authority. It is
also the grade that must meet strict standards prescribed by the COSC
(Contrôle Official Suisse des Chronométres - Official swiss
chronometer testing institute)Differences between the Grades Of The ETA 2824-2
STANDARD GRADE AND ELABORATED GRADE
Mainspring - Nivaflex NO
Collet - Nivatronic
Balance - Nickel gilt
Hairspring - Nivarox 2
Balance Staff - Epilame-coated
Shock protection - Etachocs
Pallet Stones - Polyrubies, Epilame-coated
Hairspring heat treatment - EtasableTOP GRADE AND CHRONOMETER GRADE
Balance - Glucydur gilt
Collet - Nivatronic
Mainspring - Nivaflex NM
Shock protection - Incabloc
Hairspring - Anachron
Balance Staff - Epilame-coated
Hairspring heat treatment - Etasable
Pallet Stones - Red ribbies, Epilame-coatedThe main reason manufacturers are moving away from ETAs is because they got bought by the Swatch group who are restricting supply of parts and thus controlling who can/cannot service a watch. If Tudor can no longer service their own watches in-house it fucks their brand. Swatch Group knows this.
freddo
Yeah, tbf I don't think there's much of a difference, it probably is marketing/brand perception more than anything. Have even seen it suggested that some Sellitas actually are ETA kits, merely assembled by Sellita.
You do read about the rotor bearings being noisier and/or less reliable on the Sellita autos, and that's one part that does look visibly different from what I've seen. I'm no expert or watchmaker though, obvs.