Originally Posted by
Old Farmer
I found a Trek T200 that a couple had been riding for five years ... The owners bought it used and are unsure of its age
You can probably come really close on the age by searching the Vintage Trek site.
1995 brochure -- for instance -- last page has the data on the tandems from 1995. Other links there can be searched for brochures from earlier years.
But, simpler still (and will get you within a year or two), what color is the bike? With that knowledge, look at
Trek models and colors and scroll down near the bottom to find the T200. As I understand, Trek built a lot of tandem frames (same frame for the T100 as the T200), hung them in the rafters, and then painted a batch each year, until they needed to braze some more. Between the color names and photos which may appear in the brochures, you can possibly decide what is "lunar" and what is "Saturn Silver".
Hope this helps.