I was thinking cracked die looking at it. Is that lower part of the "R" in dollar missing as well? It looks like it says "DOLLAP". I can faintly see Dollar and the other missing info like it was struck, but not hard.
Cracks and Cuds
Dies subject to excessive pressure or that are worn will sometimes develop cracks. Cracks appear as raised irregular lines that can distort legends and other parts of the coin's design. When a piece falls out of the die, coins struck from the damaged die show a raised lump or cud where the design is missing. Value depends on the size and placement of the die break or cud.
Coin Die break Cud
Bicentennial Half Dollar 1976 $4 - $8. $25 - $350.
appears to be a struck thru heavy grease error which would explain the missing design and also the craterlike shape in the middle , cracks or die breaks grow from the rim in, need better pics , either way small premium if any