I cut the hubs out of an old pair of knackered track wheels yesterday, and was surprised to discover, on removing the lockring, that the (Campag) sprocket has an Italian thread - 35mm x 24tpi.
The rear hub has a single groove milled between the base of the sprocket thread and the flange that I haven't seen on other similar hubs, and I remember reading that at one time Campag used a pattern of milled grooves to identify the thread. Can anyone tell me more about this marking? The cone locknuts are dated 1977. As close as I can measure, the hub has a BSC thread, but of course BSC and ITA are very similar.
Incidental points. The bearings on this hub were set so tight that I'd assumed they must be destroyed. Not at all. Not a mark on the cups or cones, and with fresh grease and a little adjustment they're like butter.
Also, it turns out I've been riding an aluminium sprocket without even knowing it. I've always bought steel, but this sprocket was on the hub when I bought the wheel and I've been waiting for it to wear out. It's been incredibly durable.
Calmes dans le demi-jour
Que les branches hautes font,
Pénétrons bien notre amour
De ce silence profond.