A few months ago I seem to recall someone wanting to create some kind of list or dossier on Yamaha FG series acoustics. I pointed out at the time that it was a bit more than the 75, 140, 150, 180, 200 etc, comprising many, many models. Anyway, I just stumbled on a (complete?) list of FG models on Wikepedia. It's actually a list of all Yamaha instruments (not just guitars) made over a period of many years - I noticed some from the 1940s. The FGs are about 40% of the way down the page. Interestingly it identifies the colour of the label; red, orange etc.
http://en.wikipedia.org/wiki/List_of_Yamaha_products