You'll know just as soon as you look up the serial number, but I'd start looking at 1981/82 models. The 1983 paint scheme changed to include the seattube panel color on the headtube as well, and in 1984 they made everything ugly. The paint/decal scheme in 1980 was also significantly different than yours but since the 1981 catalog doesn't show pictures or list colors you're on your own. Offhand, I'd guess 1981/1981.5 model 610 frame, which could have been built up with two different levels of average Japanese parts or with Shimano 600EX (arabesque, model 6200).
I have a thing for old Treks
. I've had seven so far and I just rebuilt a 1980 414.