I can't really tell a difference, the catalogues say that later models have lighter alu freehub bodies and lighter nuts on the axle, but the hub bodies look the same.
I think the later models had the asymmetrical rear rim, but thats just a wild guess. so if your rear rim is syymetrical, means its older model.
so here's a catalogue from 2007
https://www.campagnolo.com/media/files/035_294_Katalog_Laufr%C3%A4der_Campagnolo_2007.pdf
an here from 2004 (see from page 52)
https://www.campagnolo.com/media/files/035_298_Katalog_Campagnolo_2004.pdf
I can't really tell a difference, the catalogues say that later models have lighter alu freehub bodies and lighter nuts on the axle, but the hub bodies look the same.
I think the later models had the asymmetrical rear rim, but thats just a wild guess. so if your rear rim is syymetrical, means its older model.