Hello Niels, welcome to the forum. Your friend has a naval officers sword, or Kai Gunto, which looks to be in decent shape. Value will depend on the quality of the blade, which we will need more photos of to determine. There's a instructional guide on how to safely remove the handle to check the maker:
These are often fairly crude and can vary from having real old blades to oil tempered pieces, it would be interesting to see if you can get the nut off for a picture of the tang. For $5 it's a neat bit of history.
Unfortunately what you appear to have is a relatively recent sword (late 19th century to early 20th century) where fairly poor pieces (by Japanese standards) were made for export to foreigners. They often feature elaborate (but simple) Koshirae that would appeal to the foreign buyers with little knowledge who bought up all sorts of Samurai wares to decorate rooms or whatnot.
There are multiple stories of collectors doing just that and being jammed up for hours. The reason some collectors have great success with this method is the prior knowledge and co-ordination with an experienced dealer beforehand, just rocking up to Narita airport with a sword and a prayer is ill-advised.
It's somewhat curious how some general tassels age differently, a friend brought over the middle one where the bullion stitch is barely visible from oxdisation: