Article date: Aug 1977
Article title: A new kind of cipher that would take millions of years to break
Mathematical Games column? Y
Book: 13. Penrose Tiles to Trapdoor Ciphers
Chapter: 13. Trapdoor Ciphers
This data confirmed? yes
Notes
Peter Rowlett (27 August 2022):
Peter Rowlett initial guess (Uncertain) Next chapters refers to this as August 1977
Peter Rowlett (4 November 2023):
I have seen this chapter and column side-by-side and they match.