1900–1920 Better materials

During the 20th century, the mechanical design of the watch became standardized, and advances were made in better materials, tighter tolerances, and improved production methods. The bimetallic temperature compensated balance wheel was made obsolete by the discovery of low temperature coefficient alloys invar and elinvar. A balance wheel of invar with a spring of elinvar was almost unaffected by temperature changes, so it replaced the complicated temperature compensated balance. The discovery in 1903 of a process to produce artificial sapphire made jewelling cheap. Bridge construction superseded 3/4 plate construction.