Thanks for your detailed reply, which unfortunately confirms my confusion as it contradicts what I'm seeing.
IOfmega - > Zeus -> ISO -> Campy - >JIS read out from Sutherland's 6th Edition on the tendencies from smallest to largest end sizes.
This is what confuses me, from the above that would suggest that if it's ISO then it should be smaller than a JIS BB, but it's not. When I put one of my newer DuraAce FC-7410 JIS crank arms on it and then put the same crank on a JIS BB then is goes on further by 2mm on the JIS BB. On the Old ISO Shimano BB the crank arm sticks out 2mm more in comparison. Therefore the ISO BB must be bigger as the crank doesn't go on it as far. It doesn't tally with what is written in book and on the web
This is why I question if the older Shimano ISO is in fact the fattest BB.
Ignoring the axle, what's the shell ?
English (Their default), Italian or French ?
and back to the axle, what's stamped on it ?
Well, the shell is 68mm, French 35xP1, Axel 68=w=112. Date code is FL which is 1981/Dec.
BB-7200 came in 112mm length (ISO) and '68 W 111' on the axle (classed under 'old-double')
Could be this but has 68=w=112
on the axle.
BB-7400 came in 112mm length (Campy) and should have '68 W 112' or '68-W' markings on the axle
BB-7400 was 1985..( http://velobase.com/ViewSingleComponent.aspx?ID=F3075BAA-C7B4-4B22-B6DE-821D7D7B7B97&Enum=119&AbsPos=8
) Can't be that, it's too new.
Ultimately I'd like to get a sealed cartridge BB to replace this odd cup and cone, something nice like a Royce or Phil wood. But at the moment I can't order anything as I'm unsure what to ask for. If I order ISO I'll get something that resembles Campags ISO tapers, which from the above would be way too small...