With cantilever brakes, it isn't a 310. For 1984, the 210 also had side pull brakes, cantilevers came later. It also looks like it could be a 1986 210, which has specs similar to the 1984 610. 27 pounds for a touring bike isn't bad, the frame is thicker to support the extra weight of the bags. I'd say it's worth $75, unless it looks really bad in person. You could build it into a pretty nice bike.
http://3.bp.blogspot.com/_whtVpXkKwl...0-h/img061.jpg
http://2.bp.blogspot.com/_whtVpXkKwl...0-h/img105.jpg