Mid '80s from the decals. And I'd say a safe interpretation of the serial number on the BB shell is the last number "6" equates to 1986. In fact it might be a date and month code for June 1986. Look for a small 4 digit stamp in the headbadge. If the last number is a 6 this confirms it is an '86. The "G" stands for Giant Bicycle of Taiwan.
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http://www.trfindley.com/flschwinn_1...986Ltwt22.html