Steel-Junky writes:
"First of all I believe those to be Kai Gunto mounts... which are different from Shin Gunto mounts. If I'm not mistaken Kai Gunto mounts were Naval mounts. Most Shin Gunto mounts have the brass tsuba with the little heart type cutouts in the corners while the Kai's had an oval tsuba usually with a copper rising sun type plate on top and bottom. "
Exactly! Note the little "anchor" stamp on the tang: this denotes Naval issue as does the Kai mounts... mounts DO MATTER in military Japanese swords. They speak of who the sword was issued to and the rank of the person who wore it. It, as with any knife could be/can be/was monkeyd with perhaps but thats another matter. Originally, these mounts, scabbards and tassles were significant of rank and duty.
I'd bet it is also, as were many marine blades both Royal Japanese Marines and Marine Landing Force, made of stainless steel. See how bright the blade and tang? ... like the day it was made. These date from at least 1937 or perhaps earlier; most are unsigned so your blade may be quite valuble really. I passed on one at the last show for $700 not as nice as yours.
m