I would NOT write it off: that's not a unicrown fork, it's an internal-socket style ala the Cinelli full-sloping crown. So it has a much larger (hidden) surface area for brazing contact than just that seam...and the seam looks like it's had time to rust along the outer gap plus looks like it has chrome along the inner: like it's been present since the fork was plated and only opened up (or chipped the plating) when it was smacked.
I bet it can be straightened and returned to service with just a bit of touch-up on that line of rust.