What makes bisecting die cracks interesting is that so many bisecting die cracks occurred in 1864, and they appear on bronze planchets. This anomaly seems counter intuitive, as the copper-nickel planchets are harder than bronze and cause the dies to fail prematurely.
Rules for attribution of cracked dies:
All bisecting die cracks are attributable. Crack must be visible in the center, or very near center, of the die and extend to either rim.
“Shattered” dies that exhibit several cracks over a substantial portion of the die.
“Round-a-bout” die cracks often go from one side of a coin to the other, but not through the center. These are U-shaped or circular.
Once a crack becomes a cud, it will also be given a CUD listing