Here's a link to a post with a couple of 1960s newspaper articles about the production of TTTT. There's some interesting stuff in them, particularly the first one, which describes how imposters were prepped for their appearances. Among the details covered are how imposters were to answer questions whose answers they didn't know and what types of questions they might expect from specific panelists.
https://tralfaz.blogspot.com/2019/12/behind-scenes-at-to-tell-truth.html
