Hmmm - now I am having doubts, It was definitely before the -400 series and the aircraft in question was an oddball with all of the passenger labeling such as seat instructions in Chinese/Japanese script which means that it was either on lease or bought secondhand. It might well have been a -200, memories of the 1980s tend to be a tad vague. I have memories of looking out of the terminal windows at Smuts before boarding and noticing a long top deck which would suggest a -300 but I could very well be confused.
Was there a -200 with the stretched upper deck ?.