Shimano 600EX was 1978-1983, so it's in the right era and presumably post 1981 based on the decal. The overall picture is really small but the frame characteristics such as top tube cable tunnels, braze-on shift bosses, down tube bottle boss, cable routing under under BB shell, would all be appropriate for circa 1982-1983. The only component that can be reasonably identified in the pictures is the headset, as it is aluminum, with the scalloped nut. It does appear to be 600EX and not later New 600EX version.