I found this cartridge case in a field in Hampshire, England. Does anyone know what it is or what would have fired it? It appears to be brass with a rough lip (probably damaged). Clearly much shorter than a normal cartridge of this size (21mm from base to ragged top. Also no rim or groove for extraction. The base is 28.5mm across +/- 0.5mm. Possibly damaged ! WW2 20mm AA or aircraft cannon cartridge? Picture attached.