Excellent! Sorry I missed your earlier post with the information.
So to correct what I said in my earlier post and add additional information-
The stencil mark on the cartridge case ZG22SJ43, ZG = Blind Loaded & Plugged (BL & P) cartridge (NO explosive material and NO tracer).
SJ43 = U.S. Navy loading facility St. Julians, 1943.
Black paint on the projectile indicates , with this type of projectile, a BALL projectile (contains NO explosives or tracer element) which goes along with this being a BL & P cartridge.
The MK-3-32H9-43 identifies the projectile as a MK3 projectile (with false nose fuze) manufactured in 1943.
The projectile in the case is probably original to the case.
From the headstamp (stamped markings on the bottom of the cartridge case) the B in a circle indicates the cartridge case maker Bridgeport Brass Co., Bridgeport Conn.
So what you have is a 20x110mmRB Oerlikon cartridge, practice loading, U.S. Navy, WW2. This type of cartridge was used for practice firing the Oerlikon gun.
Hope this helps.