E60058 WWII German U-Boat periscope diorama – DID Corp.
TIL That WWI German U-boats were so difficult to combat that British sailors were ordered to try and break the periscope with a hammer to stop them. : r/todayilearned
27 photos et images de U Boat Periscope - Getty Images
German Periscope & Gun Barre Set for U-Boat Type VII (Plastic model) - HobbySearch Military Model Store
File:Periscope in a German U-Boat submarine observes a battle, WWI (33102861221).jpg - Wikimedia Commons
Atlantic Ocean Circa 19421944 World War Stock Footage Video (100% Royalty-free) 1973110 | Shutterstock
The Hunt for the Notorious U-Boat UB-29 | History| Smithsonian Magazine