The bell you have is likely from the early 20th century. The markings "O S CO" stand for Ohio Stove Company. The number 4 likely indicates the size of the bell. The "Hillsboro, O." marking indicates that the bell was made in Hillsboro, Ohio.
The value of your bell will depend on a few factors, including its condition, size, and rarity. Generally speaking, bells from the Ohio Stove Company can range in value from a few hundred dollars to several thousand dollars.