David,
I might be interested to see your catalog scans, because what you've said doesn't exactly correlate to what I remember. As I recall, the EX hubs were actually cassette only, as were the Direction-6 EX hubs and the AX hubs. Only when the 7400 group came out was the screw-on hub again offered. After AX, the 7400 group represented a big swing back toward conservatism on the part of Shimano. Other than the obvious addition of SIS, which turned out to be a very significant improvement, the 7400 group was more or less modeled on NR/SR parts. There were lots of little "improvements" over the Campy offerings, and some relatively minor features, like the low profile pedals, were substantially different from Campy, but overall the group was pretty conservative, at least relative to AX.
I may be wrong about the lack of a screw-on EX hub, but I think it was the addition of the cassette that defined the EX hub. Other than the addition of the cassette (a major differece) the only difference I recall is the QR nut. So, a screw on EX would have been just an original DA with a different QR. If I'm correct here, I suppose the real question would be whether Shimano kept making the screw-on DA hub after 1978, slappping on an EX QR nut and dropping it in a different box.
Actually, it seems that early in the EX days, Shimano played a little fast and loose on the packaging. I've seen some NIP DA spare parts in EX packaging.
Tom Dalton Bethlehem, PA, USA
CR timeline hubs were made in both freewheel and freehub variants (I have catalogue scans if anyone needs to see them), and I have post CR ~'86 Dura Ace 7400 series hubs in both freehub and freewheel versions. I don't think Dura Ace was exclusively freehub until ~'88-'89 or so.
David -- David Bilenkey Ottawa, Ontario, Canada
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