Originally Posted by
LazyLegs
bikes have had a pretty slow evolution between end of WWII and start of the 90's
You have much to learn.
If you have a particular frame on your hands, it might be worth sharing that, or focusing your research on what was available at that particular point in time. Once you're familiar with that, it's relatively easy to add to your knowledge of how the groups evolved to that point, and how they continued to evolve from there.