Soviet semi-automatic carbine designed by Sergei Simonov for 7.62x39 cartridge and known abroad as SKS-45. Immensely popular both in CIS countries and in the West, this weapon is still in active service in some countries in form of various copies and modifications. This particular specimen comes from extended storage warehouses of Tula Arms Plant and haven't yet undergo the civilian weapon normalization procedure.
The Escape from Tarkov version of the SKS is probably a civilian version, as it does not have a bayonet attached to the underside of the barrel that the military version has.
The SKS Carbine is present in Escape from Tarkov's predecessor, Contract Wars, a PvP multiplayer game also by Battlestate Games, as a tier 6 assault rifle.