A pocket watch is a timekeeping device designed to be carried in a pocket, typically attached to a chain. It features a round case that houses the clock mechanism and a glass cover to protect the dial. Pocket watches were popular from the 16th century until the early 20th century, often used by gentlemen as a fashion accessory. These watches usually have a winding mechanism, requiring the user to manually wind the spring to keep it running. Many pocket watches are intricately designed and can be valuable collectibles. They are often associated with historical figures and events, making them significant in the world of horology, the study of timekeeping.