Maybe it's a post war East-German product? They took old frame shapes and made their own working class paradise version?
Maybe you should reconsider if it's worth restoring at all? I really do like vintage bike restauration, but I believe it's more rewarding when it's a bike that started it's life as a nice and durable bike, and lots of those were made in Germany. I'm not saying this has never been a nice bike, but I would want to find out before I decided on restauring it, and otherwise find a better bike to restore.