Das Sammeln von D&P Höhenrechenschiebern

A very special item for slide rule collectors is the “Position Line Slide Rule” with the German name “Höhenrechenschieber”. This article deals with some practical aspects of collecting these items.
Restricted to the German devices produced by Dennert & Pape during WWII using the codename GWR and later on with the brand name Dennert & Pape,  three models HR1, HR2 and MHR1 were found.