thanks robbie.. i didn't realize there was a blue marble in 1988
It looks like the Blue Marble in 88 has the newer font used on the rest of the paint jobs in 1989
The Ironman model name was dropped in 1990, and WSI decided to merge the Centurion and Diamondback brands. For the first few years, Diamondback brand road bikes featured prominent "Centurion Designed" decals. The "spiritual successor" of the Ironman Master and Expert are the Diamondback Master TG and Expert TG. The geometry is clearly more relaxed, but the "Master" and "Expert" names still lived on, as did the marble fade paint jobs. The Master featured 105 instead of 600.
1990 Diamondback Centurion Master TG (made in Japan)