I think that is a US gun at the Aberdeen Proving Ground, based on the old 12 inch on a disappearing mount in the background.
The German Paris gun had a barrel support. For pictures Google "Pictures of the German Paris Gun"
I missed the fine print, but;
The picture from the German Army archives reads "798px-Bundesarchiv_Bild_102-12507_Amerika_Kstenbatterie_Beim_Aschuss.jpg".
I do not read German, so I still think is an American gun at the Aberdeen Proving Ground