Identification German WWI Artillery Shell casings brass and steel

Hello and thank for taking time to read this. I bought two shell casings at an online auction, one brass one steel, they seem to be from the same caliber, possibly 77mm? Any identification help would be much appreciated, thank you!

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hi I've had this large brass shell casing for quite a while , obviously I know what it is ..but I dont know what kind of artillery piece may have used such

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