I HATE WHEN THIS HAPPENS ... my earlier comment;
"It was mentioned along the way that the single hanger denotes a Kai-gunto as opposed to a Shin-gunto."
It should have read denotes a "Shin-gunto as opposed to a Kai-gunto".
... and as to your comment Andrew about how many are out there the number is no doubt in the thousands but not nearly as many as were initially produced as a rather substantial number ended up on the bottom of the Pacific Ocean along with about 85% of the Japanese fleet or so I have read.
Any decent shape Kai-gunto will fetch a couple grand these days. Those with high quality blades much more but they are few and far between.