I believe the basic idea dates to the Rice architecture of the late 1950s and 1960s [1]. Although there it wasn't just a programming language implementation tec

I believe the basic idea dates to the Rice architecture of the late 1950s and 1960s [1]. Although there it wasn't just a programming language implementation technique, but a proposal conceived as a full-on alternative to the Von Neumann architecture [2]. Tagged values as a programming-language implementation technique do seem to take off more towards the early 1970s, though, with the ex-MIT team that would produce the Lisp Machine, and the Xerox team that would produce Smalltalk, both using tagged values prominently. [1] https://en.wikipedia.org/wiki/Rice_Institute_Computer https://en.wikipedia.org/wiki/Rice_Institute_Computer [2] A somewhat later (1973) paper referenced above: http://www.feustel.us/Feustel%20&%20Associates/Advantages.pdf http://www.feustel.us/Feustel%20&%20Associates/Advantages.pd...