Mysterious (now ID'd) 30mm (28mm Pzb41) Nazi Marked Cannon Shell

Shell has been ID'd! http://www.municion.org/20mm/28-20Pzgr41.htm . it is indeed a 28 - 20mm squeezebore!. very rare!.

Unusual example, all literature I have found points to rimless automatic cannon rounds. not rimmed 30mm of any kind.

It could be a imperial caliber made under occupation in another country.
Or maybe a Squeezebore 28mm round http://en.wikipedia.org/wiki/2.8_cm_sPzB_41

primer thread matches a 1/4" BSP tap and plug perfectly.

Видео Mysterious (now ID'd) 30mm (28mm Pzb41) Nazi Marked Cannon Shell канала Aussie50