Very interesting Costa...thanks.
Interestingly, the attachment you have posted states that:
In 1973 Panhard and Saviem rolled out the first M4 (4x4) prototype designed as an armoured multipurpose vehicle showing a pointed bow design, wheel boxes at the side, and a verticle rear.
Yet, the M4 was part of the evaluation in South Africa the year before, in 1972.
The M6 (6x6) has the name Boerboel painted on the side. A Boerboel is a large South African mastiff breed, so perhaps the info that it was developed for SA has creedence, as I've not heard of this vehicle since.
Interestingly, both these vehicles are described as having suffered failures during the trials. As mentioned, the M4 managed to sink in a river crossing, whilst the M6 suffered hydraulic leaks and the failure of it's hydropneumatic suspension. The attachment in the SA prototype thread mentions that the M6 wasn't tested due to the failure, and sent back to France.
I wonder what became of it?
Below is the indistinct pic of the M6 (a model of?) from the SA prototype thread pertaining to the Ratel programme.