It is a German 88mm A-A Flak round's case. See the website below-it should tell you everything you need, as it shows a near identical case to yours.
3. Ammunition | TM E9-369A: German 88-mm Antiaircraft Gun Materiel - Technical Manual, U.S. War Department, June 29, 1943 (Lone Sentry)
"Much that once was, is lost. For none now live who remember it."
Nice early brass 88mm case