Really varied by year. Centurion, like a lot of brands, varied the quality of build and components almost every year. Most years got better and better, some went backwards. Like any vintage bike, the easiest way to date it is the component codes. Centurion is one of a long list of very good brands, that were marketing companies (had others make their bikes). Lotus, Centurion, Univega, Nishiki, and many, many more. Finding catalogs and info on these marketing brands is usually harder, but of course, they used the same components everyone else was using. So date codes are very useful, and higher quality bikes had higher end frame tubing and usually better components.

My wife has a Centuriion Lemans 12 mixte. Pretty nice for a mixte, but still towards the lower end.