Hamilton Watch Co.
1892 - present day (American production ceased in 1969)

The first Hamilton watch was produced in 1893 which coincided with the introduction of "Railroad Standards". Hamilton watches proved to be very popular amongst Railroad men as they were considered to be of superior quality, and 53% of Hamilton total production were railroad grade  watches. The "Elinvar" hairspring was patented in 1931 and was used thereafter, "Elinvar" being a shortening of "Elasticity Invariable". From 1933 until 1939 Hamilton were making Illinois watches in their factory and selling them under the Illinois brand, some of these watches carried the  "Elinvar" hairspring and accompanying solid balance wheel. In 1940 Hamilton introduced the 992B, probably the most famous railroad watch ever produced. Many people consider the 23 jewel 950B to be the finest pocket watch ever made by an American maker but the 992B proved the most popular and continued in production until 1969 when the American factory closed. From that date all Hamilton watches were made in Switzerland, and still are today although the brand is now under Swiss ownership.