Big John, there's a good book called "Old Electrical Wiring" by David Shapiro. It has a section of history and dating. Most of the K & T I have seen was from the 1800's till the early 30's, then it seems BX became the choice. Aluminum wire has been around since the 40's,but wasn't used widely till the 60's & 70's, mostly from 1965 to 1973, or the Vietnam years.
