I'm pretty pretty certain that is a 1990 Shimano 105SC group, which would be a perfect fit with the serial number format. We know the Centurion brand was retained in some other countries, even though it was replaced by Diamond Back in the USA for 1990 onwards. If tgcal checks the two character date codes on the back of the Shimano components, I believe he'll find they are are Nx or Ox codes, indicating 1989 or 1990 component manufacture.
During this period, the US models, besides being renamed Diamond Back, were using oversized, TIG welded frames on the higher end models. It would appear that the USA may have been used as a test market for new concepts, as the Americans are typically more receptive to technological changes. Rightly or wrongly, once things have been accepted in the USA, they often are accepted elsewhere in the world. Given the obvious difference in the frames, it would be impractical to use the same model name, though it would not be uncommon to have different names and colour schemes, soley due to local preferences.