Meaning of S'year, M'year, SM'year, F'year in academic biographies (S’70–M’72–SM’86–F’91)

Question: 

Reading scientific papers, I often see at the end of them, in the biographies of the authors, some abbreviations like the following: (S’70–M’72–SM’86–F’91).

I think that they are correlated with graduation dates, but I did not find any good explanation. Can anybody explain their meaning to me, and give a complete list of those abbreviations?

Answer: 

By any chance are these appearing in the journals of organisations like the IEEE that have different levels of membership? The abbreviations could indicate the different level of membership an author had during different periods, e.g.

• S = student member
• M = (full) member
• SM = senior member
• F = fellow

Source: http://english.stackexchange.com/questions/17192/meaning-of-myear-syear-etc-in-academic-biographies