In April 1966 Menck and Koehring agreed to a cooperation and Koehring took over the shares, which had been held by the family Menck.

The Koehring Company was founded in 1907 and offered a great varietity of construction machines of all kinds.                                

Menck was forced to sell the Koehring excavators from 1968 onwards.                                                                  (These types were called with Menck:  M 110 CD, M 70 H, M 120 H, M 150 H, M 150 H/M 300 H Skooper,    M 350 H).

It got obvious quite fast, that these excavators weren`t able to cope with the challenges European construction sites brought. They were build too weak. One disadvantage i.e. was, they had to be operated by two men (driver and one man for greasing). They didn`t fit to the until then well-known Menck-standard.

These excavators caused guarantee-cases of an unknown dimension to Menck. And a lot of the very good reputation Menck had, was gone. Therefore Menck try to do something against this development. In 1970 Menck was allowed to construct own hydraulic-excavator. The first one the M 500 H was a very good and strong one, but it appeared on the market too late. The customer were already buying O&K, Liebher etc.