Might be a lamination?, is the "crack" raised or inset?.
It's an inset. not terribly deep though, but deep enough to expose non-burnished surface and start the oxidation process anyhow.
Almost as if it cracked the Planchet at striking from the top down view, I have seen some very similar before. Not sure if I might have one just about the same in the stacks somewhere. Looks familar for sure. I am thinking the one I have in mind is from about this same era...
Dollar, that coin looks like the line is raised rather than mine which is inset. If it is raised you've got a *great* example of a die crack. I think transt4 is right about my coin, that it resulted from a split planchet. You've got a beaut, though.