If the suspect coin was really struck a second time inside the collar, it should not have rim damage, including flattening. Notice the flattening of the rim on the suspect coin, yet the genuine double-struck flip over in-collar 1942 cent on the right does not have rim flattening anywhere on the coin.
A coin's grade indicates its general condition and amount of wear. The higher the grade, the greater its value. The coin grading standard is the American Numismatic Association's 0-70 point numeric system, also called the "Sheldon Scale."