Hi Roman, your sword is out of polish, which makes things difficult.
These are just observations.
Antique koshirae, good start.
Nakago dont look too old, mekugi-ana clearly drilled, and the Bo-hi stops where it should do, so im suspecting its perhaps a late Mumei sword, 1700,s onwards.
I find it difficult to see grain in the sword, which is a concern, but maybe just tightly forged?, think I see a little open grain.
Bit of a nasty rust spot, otherwise seems ok.
Nice Seppa
Asi said, just observations from pictures which isn't necessarily fact , sorry cant be of more use.