I just received a 90's Schwinn Traveler frame in the mail. There is a screw on the inside of the drive-side seat stay a few inches above the drop out.
The only reason I can think of for it is mounting a chain guard, but I've can't find any pictures of one with a chain guard, there isn't a place to mount a chain guard on the seat tube, and there isn't one in the brochure picture.
Am I missing a really obvious purpose for this screw?