German WWI Artillery shell casings brass and steel Identification

Hello and thanks for taking time to read this, I have two artillery casings, one brass and one steel that appear to be the same size, can anyone confirm that caliber? 77mm? Too, did Germany resort to steel late in the war? Thank you!

world war one - WW1 shell case markings - History Stack Exchange

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I was told y'all might be able to help ID this shell casing. I know it's German but that's about it. Can anybody tell me anything else? : r/EOD

Large calibre markings (The Western Front Museum)

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