But there were Series 1990 $20 notes issued. I even messed up in an earlier post by assuming the OP was correct instead of looking at the signatures. Once you see the signatures, there should be no question regarding the series
Series 1990 was the old design. and only had a 10 character serial number vs the 11 character numbers from series 1996 to present. Note was indeed printed in June of 2000.