Split Planchet Mint Error
Split planchets usually occur after the strike and the coin will weigh less with a grainy appearance; the splitting can be partial, with a “hinge”, and is referred to as a clam shell.
Value depends on the denomination with common denomination dates worth around $40 to $70 range if dramatic enough and can climb as high as $800 if it’s a Morgan Silver Dollar. Furthermore there’s a three cent nickel that split and broke that sold for over $2,800.
Image courtesy of Heritage Auctions