4¾ inch diameter brass cased aneroid with a milled edge bezel. This type of bezel usually signifies an early aneroid barometer (invented 1844), and this fact is corroborated by the positioning of the hole for the adjustment screw on the reverse - at 6 o'clock instead of 3 o'clock for most - and by the serial number of the dial 6357.
This example has the earliest form of mechanism, with a printed card dial in French, in centimeters of pressure, all in perfect working condition. It also retain its original lacquer.
All early aneroid barometers were made in France, where they were invented, although so many were made for the weather-obsessed English, that many have English lettering with inches of mercury scale.
I always have some of these very early aneroids available, some with the name of the first maker/retailer, "E.J.Dent" and "Paris". They occasionally come in a polished mahogany or rosewood box with a front window, and have a dard dial, as this example, or a silvered brass engraved dial, with or without a curved red-alcohol thermometer. There is usually a printed number on the scale, up to 25,000, and this helps with dating them. The earliest I have seen had a number in the 300 range, about 1847
Diameter 4¾ + ring
Date C. 1850
Price range: $300-800