I saw where you posted this elsewhere and i was going to say that I don't see anything, the obverse looks fine to me. Then I looked at the reverse. Definitely a severe crack. A most unusual one as well. Normally when you get a crack this severe it extends to the edge of the die and can become a retained cud or even a full cud. In this case though instead of the outer piece breaking off and falling away it looks like the inner portion of the die has sunken. It shows the distinctive appearance of a retained cud, different field levels on either side of the crack. But instead of the outer portion having the higher level from where the broken piece shifts down as it prepares to fall away the inner side of the crack shows the higher level.
Is this a case of die sinking from whatever cause? It's a cool find regardless. Oops! Just saw the die sinking comment after my third reading.
