20mm Unknown Projectile

Can anybody identify this 20mm projectile? I have two the same.
Looks like someone has removed the cap from the nose?
Steel driving band. Tracer cavity is 33mm deep. One has a brass plug.
Both are 76.2mm long.
Both are stamped: 146 304 10

Which 20mm cartridge? Manufacturer & country?

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Markings and iron bands remind me of post war Oerlikon / Rheinmetall types(AA/AT).
Definitely looks like the windshield has been removed,possibly to remove the I from API?.

The driving band is not steel but most likely sintered or soft iron.

Are you sure this is 20mm?.
The images match the RARDEN 30mm L5 APSE projectile,minus windshield.

No mistake- it is a 20mm projectile. I was hoping the print and shape would make the identification easy. I hate finding damaged items. Ron.