The value of a US Coins 20th Century coin set can vary depending on the condition of the coins, the specific coins included in the set, and the current market value of the coins. As of 2022, the value of a complete US Coins 20th Century coin set in good condition can range from around $100 to several thousand dollars. Some rare or valuable coins included in these sets may include the 1909-S VDB Lincoln cent, the 1913 Liberty nickel, the 1921 Peace dollar, and the 1943 steel cent. It is important to note that the value of coin sets can fluctuate over time, so it is always a good idea to consult a reputable coin dealer or appraiser for the most accurate valuation.