Definitely internally brazed, as previously suggested. Downtube cable stops for stem shifters in conjunction with dropout eyelets and single set of water bottle bosses makes it an entry evel model. I can't see top tube cable tunnels and am not sure if that is a cable stop under the chainstay or a blemish on the wall. Maybe somebody was in the middle of drewing for a fixie/ss conversion? Regardless, it looks like a mid-1980s Carbolite frame from the P4/P6/P8 family. These models all used the same basic frame with varying components. However, if the forks are OEM, I'd say a 1984 P8 is the best candidate.