Thanks for the comments guys. In one of the links provided, it was mentioned that during the occupation of Belgium in WWI (by Germany), that Pieper was under German control. I wonder if this gun was manufactured by Pieper for shipment to Germany, which might explain the presence of German proof marks on a Belgian gun. The 10.16 stamp, if it does indeed represent Oct. 1916, would inidcate the gun was made during the war.