Japanese Centurions made between 1980-1990 use a serial number format WXYZZZZ where:

W = a letter, purpose uncertain, but probably indicates a manufacturer or Centurion;
X = a number, indicating the calendar year of manufacture;
Y = a letter, indicating the fortnight of manufacture (A = wk 1 & 2, B = wk 3 & 4, etc)
ZZZZ = four digit number, probably indicating frame number during fortnight of manufacture.

Example: N4E0283 indicates the 283 frame made during the period of weeks 9-10 in 1984.

(From Sheldon Browns Excellent pages )