1862 gold dollar minted in Philly. It is a Type 2 Indian Princess. Melt value is approx. $80. Because of their small size and smaller mintages, they always carry a numismatic premium. Unfortunately, your grandfather's had been soldered to serve as a jewelry piece. The soldering diminishes the value. Without the soldering, it would probably be valued at $250. The soldering can be removed by a jeweler, but it will still show signs at the point of attachment. It would probably be worth $170. The soldering isn't horrible and can be cleaned up. At least, it wasn't holed.
The previous poster quoted a price of $170 (VF) based on 2008 Redbook. My quote above reflects the most current value as of 3 weeks via NGC.