2 Roubles

The RSFSR's tiny 1919 low-denomination notes were produced under extreme wartime pressure, with the Soviet state simultaneously fighting multiple White Army fronts and managing a currency system in near-total collapse. Hyperinflation was already rendering small-denomination paper nearly worthless before it even left the press — the 2-Rouble face value was trivial by any contemporary measure.

At just over 12 million printed, the run was modest. The watermark — a grid or lozenge pattern depending on the paper batch — is the one security feature, though the real obstacle to counterfeiting was that the notes were barely worth forging.