It's collar clash. It's caused when the obverse die hits the top of the collar and/or scrapes along its working face. The obverse die would have necessarily been misaligned toward the left at the time of the clash. Here it's slightly misaligned in the opposite direction, which is more evidence of instability.
Oooo...I've seen these on dimes and quarter too, cant remember if I've kept any. Will have to check and see.
