Let’s talk about movements.
The movement is the engine of the watch. It keeps time, it drives the hands, it powers every complication. The case and the dial are the clothes. This is the body.
When a brand needs one, it has two ways to get it. It can buy from a specialist supplier, or it can design and build its own.
I like it when a brand builds its own. It has to control its own quality, its own tolerances, its own supply of parts. And it has to make choices. The finishing, the architecture, the shape of the rotor: those choices become the signature of the house. I open a caseback and I know whose work I am looking at.
A movement made for one watch can also do things a catalogue movement cannot. It can 
be thinner. It can run better. It can carry a complication nobody else offers.
But there is a price, and it lands on the owner, not on the brand. Servicing is often tied to the house that made it. The parts sit there, the knowledge sits there. So it costs more and it takes longer than for a third-party movement.
So why should this matter to you when you buy?
In-house usually means a longer power reserve, an accuracy that is better documented, and more care in the finishing. That is real.
But in-house does not automatically mean better. A supplier movement, well executed, will beat a young in-house movement that has not proved itself yet. I see both on my bench. What matters is how the thing is made and how it has held up over time, not the words on the plate.
In the workshop we service any kind of movement, in-house or supplier. Vintage above all.
— Renaud-Louis Chavanis, Amplitude, Sheung Wan