I'd like to revisit Zuke's contribution and continue working with Howie with what we've found in two accounts on Ludwig Schwarzschild:
"The note is signed "Uncle Karl".
"The captain and crew of the commercial submarine "Deutschland" were heroes in Germany.
"Momentos of the boat's first voyage were available to the public.
"The sender of this card wasn't necessarily connected to the crew but it is known that one crewman, a mechanic Ludwig Schwarzschild from Massenheim, was a distant cousin and friend of the Löwenstein family.
"Can anyone help pick out Ludwig Schwarzschild in the group?"
"The inscription says: "Captain Koenig with his officers and the crew on board of the freight submarine Deutschland after entering the mouth of the river Weser."
Source: ViewMate - Image Archive, Image 21654 - Do you recognize? - Germany - Wallau, Hessen-Nassau - Lowenstein and Schwarzschild - Circa 1916
2. "The German merchant submarine Deutschland brought more with her than a thrilling story of the sea to Joseph Schwarzschild, representative of Goodman & Cobrin [625 Broadway, NYC], manufactuers of infants wear, to whom the arrival of the undersea liner meant also the arrival of a twenty-two year old brother, who is engineer of the vessel. Mr. Schwarzchild visited his brother on Sunday last."
The Corset and Underwear Review August, 1916, Page 80