https://en.wikipedia.org/wiki/Industriewerke_Ludwigsfelde 
In 1959 IWL replaced the SR 56 Wiesel with the SR 59 Berlin. 
This shared the same bodywork as the Wiesel but had well-upholstered 
separate saddles for the rider and pillion passenger.[11] 
Also in 1959, MZ introduced the RT 125/3 motorcycle, which had not 
only a slightly more powerful engine but also a four-speed transmission. 
IWL specially requested that the version of the RT 125/3 motor made for 
the scooter be bored out[7] to 143 cc, which increased power output to 7.5 bhp

https://en.wikipedia.org/wiki/MZ_Motorrad-_und_Zweiradwerk
1962 Manufacture of the ES 125/ES 150 begins. 

http://www.mz-zschopau.com/about-mz.html
1962 Manufacture of the ES 125/ES 150 begins. 

http://cybermotorcycle.com/euro/brands/mz-history.htm
1962: The RT production ends.