When did Rolex develop there first in-house calibre

[Omarion07]

I know that historically, Aegler were manufacturing movements for Rolex but they were supplying Gruen with movements as well.
It wasn’t until 1935 that Aegler started manufacturing movements exclusively for Rolex and the name of their facility was changed to
“Manufactre des Montres Rolex SA”. But at that stage the factory was still owned by the Aegler/Borer family.

So my question is as follows: were the movements produced in that facility following the name change considered in-house or were they still Aegler calibres?
If it’s the latter then when was the first fully in-house Rolex calibre manufactured?
According to Millenary watches, the 1560 movement was the first in house calibre for Rolex. Is this true? What changed in 1957?
Or is it only in 2004, when Rolex purchased the facility from the Aegler family, that Rolex movements were truly considered in-house?

https://millenarywatches.com/rolex-caliber-1560/



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