It has attached rear brake cable tunnels which were reportedly introduced for the 1978 model year. Also, in 1979 they added an open format date code to the top, drive side of the seat tube. It should tell you the exact manufacturing date. If it's not there, then it should be a 1978 by virtue of the cable tunnels. Here's a link to fairly exhaustive ALAN dating guide; https://www.dcisite.be/en/artikel-info/alan-guide