Thanks everyone, most helpful. And it's nice to know that like today a lot of this seems down to style and fad than engineering and efficiency.
For those interested, here are the auction photos of the object in question, a 1979-80ish (guestimate, serial no. is 1479, anyone have a more defined date maybe?) Alan Shorter frame by Barry Chick. I think the colour scheme is pretty cool!
http://www.wooljersey.com/
or
Peter Kohler
Washington DC USA