15cm shell case...is it Japanese?

I have recently aquired a cartridge case that i am unable to readily identify…perhaps someone can help…it is made from brass and the inside neck measurement is 149 to 150 mm (it is slightly out of true)…the length is 550mm and the rim diameter is 178mm…there is a small headstamp at about 10o’clock… K19 DS 6/19 plus an anchor including 2 wavy lines plus what appears to be a Japanese or Chinese character…any clues greatly appreciated…thanks