This is a Brass Pendulum.
Weight 30grams and is 20cm in diameter; it comes in a mock velvet Pouch.
The instruments and tools dowsers use are simple. For the most part they are simply an extension of the human response giving clearer signals than can sometimes be detected without them. Pendulum: A bob on a twine reacts with a number of different movements and is often used in conjunction with charts or over a map for distant dowsing.