Hi, did you ever get any more info on your Diamondback's age? I just bought an old Diamondback Axis chromoly non-suspension, I am almost certain that it is a 1991 model (because it has cup and cone bottom bracket and they went to cartridge in 1992), and my serial number starts with a U. So if they went in alphabetical order, yours may be a 1990 or 1991? If you have Shimano components on it, and if they are the original components, this page might help you a lot to date your bike: http://firstflightbikes.com/shimano.htm