38 cm SK L/45 with armored gun shield of Batterie Pommern, Occupied Flanders, WW I. This gun was located at Clevenstraat 2 in Koekelare (Belgium). You can still see the remains and the Lange Max Museum about this gun.
US War Department
1921
Railway Artillery: A Report on the Characteristics, Scope of Utility, Etc., of Railway Artillery, Volume I, page 30, by Harry W Miller, United States Army Ordnance Department. Washington, Government Print Office, 1921. Downloaded from <a rel="nofollow" class="external free" href="https://archive.org/details/railwayartiller00deptgoog">https://archive.org/details/railwayartiller00deptgoog</a>