Damiler and Benz had each been building tractors separately prior to their merger in 1925. Benz built the world's first production diesel tractor in 1922. MB built tractors into the 1930s. Mercedes returned to farm tractors in 1950 when it acquired the Boeringer Unimog, a four-wheel-drive truck with PTO and three-point hitch. In 1973, the Mercedes-Benz name appeared on tractors again with the MB Trac. This four-wheel-drive tractor featured three-point hitches at both ends of the machine. The MB Trac design was sold to Schluter in 1980, and production ceased in 1991.