The smiley is 20 years old this week, according to a Microsoft researcher.
Mike Jones, at the firm's Systems and Networking Research Group, told news website Ananova that he discovered the original emoticon after six months of "computing archaeology".
He explained that the first smiley appeared in a posting on 19 September 1982 in a bulletin board post at the Carnegie Mellon University.
The image appears in a message which says: "I propose the following character sequence for markers :-)."
If the claims are true, the popular emoticon celebrates its twentieth birthday this week.
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