Centurions (except the Cinelli\Centurion) have serial numbers on the underside of the bottom bracket shell. One way to date a Centurion is to try to find date codes on the bike's components.
Centurion models manufactured in Japan between 1980-1990 use a serial number format WXYZZZZ with:
W = a letter, purpose uncertain, possibly 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.
N4E0283, as an example, would indicate this is the 283rd frame made during the period of weeks 9-10 in 1984. Barring a major components upgrade at some point in a bike's history, one can confirm a bike's age by the dates found on the majority of components in its groupset."