Both of the coins in the World War II set were issued because the previous metal was needed for War efforts, so new coinage were created with different metals.
1943 Steel Cent: These steel cents are U.S. one-cent coins that were struck in steel due to wartime shortages in copper. The Philadelphia, Denver, and San Francisco Mints each produced these 1943 Lincoln cents. The coins were given various nicknames such as watime cent, steel war penny, and steelie.
1945 Japan 1 Sen: Although the coins were made in 1945, the date isn't on them. The obverse design features Sakura blossoms in the center surrounded by thee kanji meaning "Great Japan". The reverse features an accounting kanji, meaning "one" with Mt Fuji in the background with clouds. They are made of red porcelain.