Call Trek, give them the S/N perhaps they can help you out with more info.

Biopace came out in the early 80's. I was in high school when a friends Bianchi had them. I'm guessing 83-84. I think Shimano quit manufacturing them early 90's. I'm guessing the bike is about 25 years old. Which doesn't matter, as long as you enjoy it. Have fun!

On edit--

A little googling and I came up with this : http://mombat.org/Fisher_Specs.htm Looks like it might be a 85-88 range. Even had that color combo in 85 http://mombat.org/1985_Fisher_Comp.htm Look at the selection of components and what was used when on his bikes for a better guess. No SIS shifting with BioPace with that paint scheme....I'm sticking with 1985.