JAPANESE WEAPONS IS NOT MY FIELD BUT HERE ARE SOME PICTURES THAT MAY HELP THE DISCUSSION.
I ALWAYS CALLED THE WEAPON YOU REFER TO AS KABUTOWARI BY THE NAME HACHIWARI. BOTH EVIDENTLY HAVE THE SAME MEANING, FROM WHAT I REMEMBER MOST OF THESE COME FROM THE EDO PERIOD WHEN SAMURAI WERE FORBIDDEN TO CARRY THEIR SWORDS IN PUBLIC. THE RANGE IN SIZE OF HACHIWARI I HAVE SEEN IS FROM 350MM TO 450MM AS STATED ON WIKI. THERE ARE PICTURES OF SEVERAL HACHIWARI/KABUTOWARI OF THE CURVED SHARP POINTED FORM AS WELL AS THE STRAIGHT BLUNT ENDED FORM. I ALSO INCLUDE A COUPLE PICTURES OF A TEKKAN (IRON SWORD) THIS WAS ALSO CARRIED IN THE EDO PERIOD FOR THE SAME REASONS AND IS APPROXIMATELY THE SIZE OF A WAKIZASHI.