Originally Posted by T-Mar

An American catalog isn't going to help. The S/N indicates a 1990 or 1991 model manufactured in 1990. In the USA, Western States Imports discontinued the Centurion brand in late 1989, marketing the 1990 road bicycles under the Diamond Back brand, which had previously been limited to ATB and BMX.

The Centurion brand was owned by different companies, depending on the country. This why Centurion survived in Europe after it disappeared in the USA. The brand owners in each country were responsible for naming and specifying the models. Consequently, models often varied, sometimes significantly, between markets. Basically, you'd have to find an Australian market catalogue to ensure the right specs. Having said, we've seen two 1990, Australian market Equalizers. Both used a Shimano 600 Ultegra group. Refer to posts #668 and 2010 of this thread.