Originally Posted by
DiabloScott
My best guess: 1986 Criterium.
Never seen anything like that fitting on the down tube, could it be for a cadence sensor?
I think you are right DiabloScott, a quick look at vintage-trek's 1989 Catalog denotes in the add on sections, you could have a Cateye Solar Cadence mount added for $3.00
http://www.vintage-trek.com/Trek-Fis.../1989klein.pdf