The period between the 70's and 80's were a virtual weight battleground between most of the big manufacturers.
Their brochures and catalogues typically listed weights for most of their sport, race and touring bikes and it did affect sales as weight weenie fever was very contagious back then. But as noted, the weights listed were inconsistent with actual weights of the bike when you weigh them yourself. Some manufacturers seem to have manupilated their wieghing process to their advantage and did not weigh complete bikes (No pedals, reflectors, smallest size frame, no bottle cage....etc.) So it was not surprising to find out when you wiegh something like a Peugeot PSV back then and come up with a weight up to 2 pounds over what is in their catalogues.
I do remember seeing some catalogues evetually adding the word "Approx." in front of their wieght numbers which must have give them a bit of tolerance with the buying public for their innacuracies.

Chombi