I did some research on this weapon and the results are as folows:
After WWI the peace treaty forced on Germany curtailed much of the military arms production.They were allowed to make sporting arms which they did.They had a large quantity of M98 Mauser rifles which they converted to shotguns by removing the rifle bbl.collar and locking shoulders in the reciever ring were bored out from the front and a shotgun bbl.fitted.Front of the bolt was bored and a special bolt head fitted.Various other changes made and the result was a handy,lightweight and low cost bolt action repeating shotgun.Most of the guns were of Geha brand,like one shown in picture above,also Geco,a brand name of Gustav Genschow & co.and another brand is the Remo.