These pieces varied greatly in size. The one pictured measures 2 feet (61 cm) long. Have seen some 13 inches (32 cm) long. They come apart at the cannon line. Some held bottles and served as status symbols. Smaller ones were often used as salts.
Although you see these in Great Britain, they were generally imported from Holland, Germany and France in the 19th century.
What were they called?
Pat.