Sword says:
備州長船勝光
Bishū Osafune Katsumitsu
Bishū is an old province name of Japan. Corresponds roughtly to present-day Okayama Prefecture. Osafune is a city famous for sword-making. Swordsmith's name is Katsumitsu. Could be much older than WW2 - by several hundred years. Don't touch the blade area (because fingerprints are notoriously bad for old blades like this). Don't try any polishing yourself, as nothing is more damaging to a blade than someone who thinks they can grind, sand, burnish, or otherwise "polish off" any defects (only to find they've damaged the crystalline structures that make these things valuable in the first place). Don't do anything more aggressive than wiping gently with a fine cloth (microfiber, like the kind used for glasses and lenses if you have any).
It could be an old family sword that was repurposed for the war. The scabbard looks similar to WW2 scabbards, anyway.
There is a forum especially for Japanese sword enthusiasts called "Nihonto Message Board". Care and handling instructions can be found there.
