What is the fine-grained topic of the following text: During the 1870s, Francillon’s choice of industrial options was proved sound and the factory continually expanded until the first third of the 20th century: in 1911 the Longines factory employed over 1,100 workers and sold its products all over the world. Only return the topic.
Expansion of the Longines factory in the late 19th and early 20th century