20x110mm Oerlikon "FSC 1045 20mm MK4" identification

[sksvlad]

I think it is made by Florence Stove Company of Kankakee, IL.[FONT=tahoma, arial] [/FONT]What kind of a round is it functionally? It has 2 empty cavities, one in the nose, another at the bottom. The projectile says: MK7 28 F lot 346, the nose cap says: MK-26-1-DDCCO-P

 

[bdgreen]

U.S. Navy Projectiles and Fuzes, U.S. Navy Bomb Disposal School, 1945