I suspect that is the top tube' right behind the head tube and we might be seeing the tip of the top head lug on the tube? Those look like cracks on the paint. Could be evidence of frontal collision damage to the frame. The paint might have also cracked at the bottom of the top tube and fallen/ flaked off, thus the rust you might be seeing.
you might want to look at a good pic of the bike from the side to see if the fork and frame might be bent. Hopefully I'm wrong, but it is good to check before you purchase....