Boker knives for sale. Boker / Tree Brand is a manufacturer of knives, including automatic knives based in Solingen, Germany. Boker knives primarily makes folding and outdoor knives. Boker has long had production facilities outside of Germany. By the 1860s the company had fractured with a branch of the family emigrating to North America and setting up plants in Canada, New Yrok and Mexico. The German and North American factories produced similar knives and used the "Tree Brand" trademark. This continued until World War 2 when the Solingen factory was destroyed and "Boker USA" took control of the trademark until the German factory was rebuilt in the 1950s. In the 60's and 70's the company changed hands several times, with the New York facility (Hermann Boker Co)shutting down in 1983. In 1986, Boker USA, was started in Denver, Colorado for US production.