It's link easy to tell Vichet and Wenger cases apart if you can open the watch and see the inside of the caseback, looking for the "Key 9" signature for Vichet or "Key 1" for Wenger. But it's not often you get to "crack open" a $300,000+ watch. link So, like link with the ref. 2499, you can start by looking at the lugs very closely.