M6? A very cool car indeed
If you donīt mind, iīd like to chip in a different perspective:

Thatīs a WW.TC (obviously

) and the so-called "Swiss Edition".
Only 50 units will be made and itīs special in that it comes with a grey dial and steel case (none of both are regularly available features).
Now the pictured piece is different from any other of that (small) edition, in that itīs a prototype and comes with a steel case of earlier design. The actual pieces will benefit from the latest improvements introduced in 2006.
So thereīs only this very one watch to be in existance.
Is it worth a premium, in case it would be available for sale (which it is not)?
Maybe so, if thereīs someone looking for an unique piece and so in love with it that he pays a premium, knowing the WW.TC is among GPīs most successfull individual models.
Maybe not, if the market doesnīt put out a premium at a given time/place/context.
The same could be asked with prototypes or unique pieces which are not part of a limited edition, such as the three-hands working model prototype with GP4500 caliber pictured earlier. Of this, only that one exists and thereīs not even a remotely similar model available for purchase.
Or other variants of the "Team Watch" (thereīs a really tiny run with a different dial, which are ultra-rare and in the hands of some very few assorted friends of Girard-Perregaux).
Long story short, in the end you
really know only down the road.
And even in this, things tend to be depending on the specific piece, the place/region of sale, maybe the prior owner and the general interest in the brand who made it. All this is flexible and to my experience doesnīt allow for easy guesses on future developments. Otherwise weather forecast would be more exact
So my personal recommendation is always to buy it only when you like it and not if you regard it an "investment".
History (and iīm much more a "vintage watch guy") seems to suggest what is a slow seller today might be the ultra-hot sought after collectible tomorrow. There are plenty of examples, recent and not so recent. And there are example for the opposite, when seemingly "hot" stuff today is moving slow tomorrow.
Therefore, the best reward most probably is the fun it brings to you; if it makes you smile, itīs probably worth venturing into it. If it doesnīt speak to you that much, then iīd not go for it.
Just that iīd not try to decide coming from a "price/value" perspective, because thatīs depending on future developments
really tough to determine.
In this, i tend to regard watches like cars; if they appreciate or hold value itīs fine, but itīs neither prerequisite nor a priority. Sure i have and had pieces that left me for less than i paid; thatīs the price of owning luxury items, while the smile they brought on my face is priceless and irreplacable.
Cheers,
Peter