world war one - What's this 1917 shell casing, more exactly

I've been gifted this vase that is obviously made out of a large shell casing. It has 'MARZ 1917' stamped on the bottom, plus other less understandable markings: 'St', 'G', '36', 'HL 25'. I'm attac

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Large calibre markings (The Western Front Museum)

Pair of WW1 British Brass Artillery Shells Dated 1917 For Sale at 1stDibs 1917 artillery shell, antique artillery shell for sale, ww1 shells for sale

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13pdr Shell Identification - Arms and other weapons - The Great War (1914-1918) Forum

world war one - What can I learn from these WW1 shell cases? - History Stack Exchange

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Pair of WW1 British Brass Artillery Shells Dated 1917 - Country French Interiors