Rick, the only Lechner that I know is still in business but it is not in Nürnberg it is in Austria in Graz and the name of the shop owner is Lechner & Jungl.Looking at the shape of the tang it is an early gun, to tell you when it was made you need post pictures of the barrel flats and action of your gun. I can confirm that your gun never had a second rifle barrel.
Marc.