A loose pile of rubles
A briefcase of rubles
Rubles are the currency in Dark Sector. They can be used to purchase new weapons at the Black Market after Chapter 4, though they can be found in every chapter after Chapter 2.
Rubles can be found in two different forms: as loose bills and a money roll, which are worth 1,000 rubles, and an open briefcase, which is worth 3,000 rubles.
There are only a set amount of Rubles found in the game, the only other way to gain rubles is to sell unwanted items. Frag Grenades work well for this if the player doesn't mind giving up some of them.