The society's activists have been charged with trawling the country to find those buildings that may now be considered for listing.
The first of the iconic buildings likely to find itself on the statutory protected list is Richard Rogers' Lloyd's Building in London (pictured).
The C20 study will begin by studying the key magazine and publications from the era, but its organisers believe that these were London-centric and are therefore especially keen to see buildings from other regions.
David Davidson from C20 described the problems of the study. He said: 'What do we really know about the totality of what was designed or built? Which representative examples should be saved? Which can we safely lose?
'These questions put me in mind of the Donald Rumsfeld quote: 'There are no knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are things we do not know. But there are also unknown unknowns - the ones we don't know we don't know.'
'Its very much the same with the architecture of the 1970s,' Davidson added. 'If you follow that.'
For more information, visit www.c20society.org.uk