Originally Posted by kiemchacsu
...I heard somewhere that some repairmen can CLA the Leica Cameras without breaking the "L" seal
I can't see how.
The seal covers a screw which must be removed in order to take off the top-cover. While certain repairs (like adjusting the shutter curtain brakes) can be done without disturbing the seal, access to the camera's internals require that the top-plate come off.
That said, the seal consists of a soft black wax plug with a scripted "L" impressed in it. Not too hard to forge if one has a mind to deceive.