Markings on bottom of shell casing : r/MilitaryHistory

Artillery shell cases, fuzes, primers and tubes. – Stephen Taylor

Large calibre markings (The Western Front Museum)

Cartridge case terminology and identification – Stephen Taylor

Any info on the markings on this artillery shell? : r/ammo

Shell casing identification : r/Militariacollecting

Help identifying a shell casing from military funeral : r/guns

Shell identification - Other Equipment - The Great War (1914-1918

Shell casing identification : r/Militariacollecting

WW1 Photos & Info.

Handloading - Wikipedia

Large calibre markings (The Western Front Museum)

5.56×45mm NATO - Wikipedia