I have pretty much concluded that the braze-on issue would do little to help nail vintage down exactly. I do still wonder if different styles of braze-on were more prevalent at certain times. For example, it would be nice to know when the chain stay braze-on first appeared and on what bicycle. Knowing something like this would prove to be a good starting place for a guy like me. Also...

Why select several different places to run the rear brake cable. On top, underneath, on the side, full casing, half casing. Is there any rhyme or reason to some of the choices the engineers of days gone by made?

Just something that interests me and there seems to be so little consensus present.