The serial number indicates the frame is Japanese, probably built by National/Panasonic, and was manufactured in March, 1984.
Originally Posted by Schwinn Bulletin 23
Bicycles from Japan have a production month letter in either the first or second position and a production year number in the other (first or second) position. Examples J677123 = September, 1976, 6J77123 = September, 1976.
Le Tour (and Super Le Tour) numbers (1978-80 and 1982 on) include the letter “S” with a production month letter followed by a series on numbers, the first one telling the year of production (8-1978, 0-1980). Example SC94653-March, 1979.
A=January, B=February, C=March, D=April, E=May, F=June, G=July, H=August, I=Not Used, J=September, K=October, L=November, M=December
1984 Specifications