It is mechanical doubling or die shift. The keeper or holder for the die was loose causing the die to move. I had always thought that it (the die twisting or moving) was on the die's initial impact with the planchet, but current thought is that it happens as the die begins the 'upstroke'.
Last edited by Bill in Burl on Tue Aug 19, 2014 8:46 pm, edited 1 time in total.
Here's at least a cousin to your 1861 NS cent; seems the legend was a real problem, mine does not have the die crack through the 'A' == notice line over BRITT == notice joining of lines at 'G : F : D:'