Campagnolo sprockets have either 4 or 8 mounting tabs. While not a hard and fast rule, alloy Campagnolo pattern bodies usually have 8 notches, while steel ones often have 4 or 5 notches interspaced with relieved sections to accept the additional tabs.
Last night a mate picked me up on some of the above - a more detailed review can be found here.
And sometimes I get caught out. Wanted a wheel for use on a turbo trainer - 32 h with a Campagnolo-style freehub so I can run an old Campag cassette and use a spare rim I've got knocking around. Couldn't find a cheap hub then found a used 9-speed wheel for less than what people were asking for hubs.
Except there was a reason for it being cheap - now I've got it, it's not 9-speed, it's 8. On the off-chance I tried a spare 9-speed body and as I expected, it won't fit into the hub.