world war one - What was this 1917 shell casing used for

By A Mystery Man Writer

Bought this shell from an antique store. Would like to know the history behind it, as in what it was used for? (The casing is about 16 and 1/2 inches in length)

Original German WWII PAK 36 Stielgranate 41 37mm High Explosive Anti-Tank Stick Grenade – International Military Antiques

Ww1 shell cases hi-res stock photography and images - Alamy

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German WW1 Rhinemetall Shell Case 1917

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Large calibre markings (The Western Front Museum)

German soldier dives for cover as shell explodes behind him at an artillery position, 1917 - Rare Historical Photos

Were the howitzer, about 100mm brass shell cases from WW1, reused or just wasted after having been first fired? - Quora

Weapon - ARTILLERY SHELL & PROJECTILE, 1917

Ww1 shell cases hi-res stock photography and images - Alamy

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