This stop watch features 1 button. This easy to use stopwatch starts, stops and returns to zero by consecutive crown depressions. Manufactured in accordance with requirements of NSN 6645-00-250-4680 but also has the added features of being water and dust resistant. Stopwatch has a fibreshell case (resists corrosion and erosion caused by acids). This stopwatch has a 30 minute register with 1/5 second divisions. Stopwatch is antimagnetic and shock resistant. This stop watch is made to Government Specifications and has 7 jewels. This watch is used in areas of high humidity and dust; it is great for laboratories and geological surveys. This stopwatch is made in Switzerland. 0 to 30 minutes (30 min. register) 1/5 sec. divisions Starts, stops and returns to zero by consecutive crown depressions Fibershell Case (resists corrosion and erosion caused by acids) Dust and water resistant Antimagnetic and shock protected 7 jewels.