There is one more area further down the bade with the same rectangular shape. It's fainter, but even larger, than the ones shown. The other side of the blade looks fine. Umegane was my first thought. But to that extent? If tobiyaki was intended, why only one side? And If accidental, what's the likelihood of getting those straight lines and sharp corners repeatedly? I don't know. It's unusual.
Thanks!
Dave D.