CLM (Climate Limited-Area Modeling [community]) here means the Climate Limited-area Modeling (community). For external data for the entire COSMO-DE domain, visit:
http://www.clm-community.eu/index.php?menuid=221&reporeid=260
According to the file run_cosmo_de[4], the coordinates are:

  startlat_tot  =  -5.0  ,
  startlon_tot  =  -5.0  ,
  origin lat    =  50.0   (calculated from pollat        =  40.0),
  origin lon    =  10.0   (calculated from pollon        =-170.0),
  dlon          =   0.025,
  dlat          =   0.025,
  ie_tot        = 421    ,
  je_tot        = 461    ,
  ke_tot        =  50

At least the coordinates should also be in the COSMO User Guide:
http://www.cosmo-model.org/content/tasks/operational/dwd/default_de.htm
The goal now is to refine the resolution and retain everything else. Beware:

• If dlon<0.005 or dlat<0.005, dlat must equal dlon to prevent a fatal error.
• je_tot must be 3000 or lower.

It took 2 attempts to retrieve just the right data, one on 2017-09-05 which tried to reproduce the Estimated resolutions of the test data, and one more successful one on 2017-09-11, called the Divided by 7 approach.

Footnotes