mavic did make there own proprietary cog/cassette spline pattern for several years but they were fairly rare. THe mavic pattern is 9-spline (like shimano) but used very different looking rounded grooves Urban legends, and things I was right to believe in... ~ tears for gears

Original campy 7/8 speed spline pattern was symetrical, no wide groove or spline. The later EXA-drive 8-speed pattern had a single wide spline to enforce cog alignment. Fortunately, exa-drive cogset will still fit fine on an early cassette body, just keep them aligned correctly for good shifting.
Cassettes and Cogs - Branford Bike - Seattle/Bellevue - Campagnolo Pro Shop Looks to me like you have the original campy spline pattern so any 8-speed campy cogset (exa-drive or original) should fit and work fine with 8-speed chorus drivetrain.

good thread on various mavic/campy spline patterns and bodies at; Mavic Helium Freehub Body