a quick google shows up an old Tanknet post - see e.g post #5 in the thread. Apparently used as a mountain gun.
http://208.84.116.223/forums/index.php?showtopic=25248
The Swiss Pak 50 and 57 (units 689,690), although also 90mm are different beasts from the Mecar/Cockerill and were primarily for anti-tank work
Andy