Don't you have any cassettes lying around to try?
If it's Shimano, seven eight nine and ten speed hubs use the same spline pattern, but the depth of the freehub body varies to accept more sprockets. 7-speed measures about 30.5mm from the shoulder on the freehub body. Eight and nine are both about 34.5mm. I don't own any ten-speed hubs, but I believe the body's actually shorter than 8 and 9 by about 1mm.
There's a page giving details of the various 7, 8, 9 and 10 speed Campag bodies here:
Broadly speaking, with Campag 9 and 10 are the same, but 8 was different.
If you could post a picture or some more details of the wheel (specifically the hub) it would be a lot easier to help.
Calmes dans le demi-jour
Que les branches hautes font,
Pénétrons bien notre amour
De ce silence profond.