Jaeger-LeCoultre

I have a '08 JLC Master Control Reserve de Marche. When tapping the case with my fingernail, it sounds as though there is something loose, like a rattle or a loose spring. What makes this noise? Is it normal operation? Any thoughts would be appreciated. T... 

... not likely that the sound is produced by a loose part of the movement bouncing around in the case. As the 2008 RdM is equipped with cera- mic ball bearings on the rotor I could imagine that the sound orignates there. The ceramics are not lubricated (u...