Liberia – History of Railroads – Mallard – $5 – 2011 – Colored Proof Silver Crown – An A4 Pacific class engine, built for speed and efficiency, the Mallard holds an unbroken record as the fastest steam engine in the world. She achieved the feat amid much publicity in 1936, and her record has stood ever since. Retiring from the high speed express services she pulled in 1963, she is now a resident of York Railway Museum. This proof legal-tender silver coin was minted under authority of the Government of Liberia from 20 grams of .999 fine silver and has a diameter of 38.6 millimeters. It comes with a Certificate of Authenticity.