This item is a unique instrument containing a compass and barometer that unscrew so both can be used at the same time. It is approximately 2″ diameter and 1″ think when it is together. The compass has a dampener. Unfortunately the barometer no longer works. There is no makers name so it’s hard to know how old it is but my guess would be early 1900s. The case appears to be plated brass. If you need more pictures or have any questions let me know and i’ll get back to you.The item “ANTIQUE POCKET COMPASS AND BAROMETER/ALTIMETER” is in sale since Monday, November 03, 2014. This item is in the category “Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Barometers”. The seller is “rebelsurveyor” and is located in Monroe, Georgia. This item can be shipped to United States.