I am selling an extremely rare Mixer which was built for the NAGRA 4S. There are special Screws on the side. These machines were made in a small quantity. In the Internet I have read, that arround 100 to 125 were made.But my machine shows the serial number 160 if a can read it right... Unfortunately I cannot test this machine because it needs 12 thick batteries... There is no connection for an external power supply. If I am able to check the functionality in the next week, I will add this information here, but till then, i sell it as not working (even if the person, whom I bought it from promised me, that it works) The shape is good for its age... Battery Contacts are very clean... It is portable, but heavy... Feel free to ask me questions.