Diamond Back began in Camarillo, CA. It eventually was swallowed up by one of the mega companies and Diamondback became one word around '97. It's pretty easy to figure the age by the components. The Shimano crankset should have a date code and, assuming it is original, that should give you a good idea of the year. Post a pic, that can help as well. I've had a lot of DBs over the years (I live 20 minutes from Camarillo) and currently have 5. I know 2 of the '92s have serial numbers beginning with "U" and at least one '92 starts with a different letter but can't remember what it is at the moment.

You can also post in Classic and Vintage. Lots of knowledge on older bikes over there.