............... If you are not aware of the takedown procedure for viewing the receiver tang date, please educate yourself on the action of the barrel band screws before disassembly, clockwise turn to loosen, counterclockwise turn to tighten.
It is a Finn [SA] and D marked Russian M91
MOSIN Nagant made at Tula in 1898. Anyways what we can see on the barrel. Receiver mark if it is also Tula and same year or possibly original to the barrel should have a small hammer and two digit year "98" marked on the bottom side of the receiver tang. That is located at the rear action screw, on the bottom side not viewable unless you disassemble the rifle and removed the barreled action from the stock. With a Finn acquired rifle, by either purchase after WWI or capture from Russia during the Winter/Continuation wars, it could be any arsenal or dated receiver over the time period those style receivers were produced. It also looks like the Finns already notched the first step of the rear sight base, which is a common Finn modification for their renumbering of the rear sights to meters.
Nothing looks out of line with the rifle from your pics. Looks like at least one front sling slot escutcheon is missing. And that is a 91/30 bayonet someone tried to put on the end of it. And as Martin mentioned about the barrel bands, observe the instruction for tightening and loosening if you decide to take it apart. Highly recommended to use some hollow ground gunsmithing bits to loosen and tighten them, that fit snugly. If one of the screws snaps, it's not repairable due to the nature of it's design and another barrel band will have to be obtained.
You will also want to be careful removing the small set screws in the stock that are pinned against the barrel bands to keep them and the handguard from sliding forward when shooting. The Finnish brad screws are delicate and sometimes can already be stripped out in their hole. Best to try to use just a bit and some finger loosen and tightening. They are normal threaded, wood screws. Right turn to tighten, left turn to loosen. That's for the wood screws only. The barrel bands are not normal loosen and tighten. Refer to Martin's original, and highlighted quoted post regarding barrel band removal! You only have to loosen them enough to slide off the stock and off the end of the barrel.