By sister do you mean it came off the same base caliber?
My guess is..sister company....within Richemont,....which includes master movement finishers like Lange and vacheron to name a few...
So the next question that pops up is that I guess Pams in-house is actually Richemont's in-house? Thus not exclusive to one single brand.
It's funny how SA always tout in-house as the selling point but when asked how much of it is in-house, they are stumped. No offense but I think this term "in-house" is just a marketing ploy. It's like proton changing the manifold and side skirt of their car and overnight they are a car "manufacturer"