Campy made a change to the freehub body, maybe 25 years ago, when they changed from a small diameter steel axle to a larger diameter aluminum axle. The thread size on the freehub body was enlarged at that time. The flange diameter must also match the first sprocket, so it could be for an 11, 12 or 13.
New cassettes for the modern hubs come with the proper lock ring, so you get a new one with each cassette. If you bought a new cassette and the threads are too large, then you have a really old hub.