I asked Vacheron's atelier cabinotiers to make me a traditonelle with MOP guilloche and they replied "It is impossible"!!!
Obviously not!
Lange had an MOP guilloche small Lange 1, that's the only other example I know (of course, Breguet has several models with MOP guilloche).
The folks at Breguet told me that the secret is to soak the MOP, could you tell VC for me?
Oh, and (this is a little bit of an obsession for me, can you tell?) I spoke at length with the guillocheur at the Patek exhibition in NYC. He told me MOP is certainly possible, but you break 1 out of 4 dials.