1988 too early?
No, I was doing OOD with Modula-2 in 1985 and C++ in 1987. The seminal C++ Programming Language by Stroustrupp was published in 1986.
Glockenspiel ported the AT&T C++ preprocessor to MS DOS to sell a C++ compiler for DOS (the back end was MS C DOS compiler). Also they worked on Amiga, Atari and Xenix versions. ALL before 1988.
You don't need C++ or Smalltalk to use the ideas of OOP / OOD, though it's difficult in Fortran :)