Orenstein & Koppel
 Orenstein & Koppel (normally abbreviated to O&K) was a major German engineering company specialising in railway vehicles escalators and heavy equipment. It was founded on April 1 1876 in Berlin by Benno Orenstein and Arthur Koppel.Originally a general engineering company O&K soon started to specialise in the manufacture of railway vehicles. The company also manufactured heavy equipment and escalators. O&K pulled out of the railway business in 1981.