In the late 19th century, manufacturers such as German toy company Bing introduced the two main types of model/toy steam engines, namely stationary engines with accessories that were supposed to mimic a 19th-century factory, and mobile engines such as steam locomotives and boats. Later, especially in the early 20th century, steam rollers, fire engines, traction engines and steam wagons began to appear. At the peak of their popularity, around the mid 20th century, there were hundreds of companies making steam toys and models. Today, companies such as Wilesco (Germany), Mamod (UK), and Jensen (US) continue to produce model/toy steam engines.