Also, another example of an "unreasonable" challenge - the "Decipher Puzzle" https://cisa.umbc.edu/wp-content/uploads/sites/468/2017/09/S... -- from 1983 to 1985.

You would think that one of the lessons of that is that someone could jump in right at the end and solve it after several clues were released. That hasn't worked with K4, which is increasing people's skepticism.