1943 steel cent coins. The copper cents differ from their steel counterparts in four ways: In an error similar to the 1943 cents, a few 1944 cents were struck on steel planchets left over from 1943. There are two explanations given for why this happened. One explanation is that steel planchets were left in the press hopper and press machines from the previous year mixed in with copper planchets. Another explanation credits the error to the production of 25 million Belgian two franc pieces by the Philadelphia mint after that country's liberation from the Nazis. These coins were of the same composition and
Eisenhower dollar proof planchets were to be used for uncirculated "blue Ikes", but these were placed in the bin for rejected copper-nickel proof planchets, intended to be shipped to be coined for circulation at Denver. The 1977 pieces resulted from pieces rejected for Bicentennial silver proof use, which were again placed in the wrong bin (they should have been melted, as the Mint was no longer striking silver uncirculated Eisenhower dollars). Between 10 and 20 of each date are known. Wexler, Crawford, and Flynn report an even rarer 1776–1976-D dollar in silver, but state that none have been offered at auction or