Article date: Dec 1975
Article title: A random assortment of puzzles, together with reader responses to earlier problems
Mathematical Games column? Y
Book: 12. Time Travel and Other Mathematical Bewilderments
Chapter: 16. The Sixth Symbol and Other Problems
This data confirmed? yes
Notes
Peter Rowlett (27 August 2022):
Peter Rowlett initial guess (Very uncertain)
Peter Rowlett (2 November 2023):
I have seen this chapter and column side-by-side and they match.