I used to collect katana. Your sword is is a shirasaya (a storage sheath) - These are often unmarked. The markings on yours likely refer to an address (probably one of the previous owners).
For a Japanese sword, the fittings (handle, guard, sheath etc…) are kind of their own thing - the person who made the blade didn’t make the fittings. They can have their own collectable value and collectors community (not yours, shirasaya were used for storage of the blade). A single sword could have had multiple sets of fittings made for it over it’s lifetime.
The markings you want if you want to know anything about the sword are on the tang. You need to remove the blade from the handle. There should be a bamboo peg holding the blade in - knock this out and the blade should come out.
If you do this, do not clean the tang. It likely will have rust or patina - it’s supposed to have this. Cleaning it may damage the sword and will definitely reduce the value (if there is any, lots of swords out there are from the Showa era, made around WW2, these usually aren’t worth that much).
Thanks, everyone, for the helpful replies! I will take another look at the handle to see if it can be easily removed without damaging anything.
I’ll also ask my MIL if she remembers anything about how it came to be in the family. IIRC my FIL’s father lived in Japan for a few years (and started a 2nd family there(!), but that’s another story. My FIL handed it to us at the start of his slide into the dementia pit, fearing he’d hurt himself, or someone else, with it.
It you can get a good image of the last part of the address, maybe there is enough information there to identify the previous owner, and from there try to work out the provenance of the blade.