The off-center and multi-denominational clashed dies are two of the rarest types of die varieties created at the United States Mint. There are only 6 verified off-center and only 6 verified multi-denominational clashed dies for all 19th century coinage. Of the 41 books the Flynn has written, this was one of the more difficult and time consuming, as it required the mind-boggling task of trying to figure out how they occurred.
The first part of the book explores clashed dies in general. This type of die variety is normally created when the working dies are in the coining presses. A clashed die normally occurs when the obverse and reverse dies in the coining press strike each other without a planchet between them. This was especially common on some series such as the Three cent nickel. It was originally accepted by most that the outline of the design elements were left on the opposing working dies from the edges of the design elements. This theory was proved invalid. The remnants of the clashing is a result of the fields being compressed. A complete analysis was done to prove this theory valid.
Off-center clashed dies required the working dies to be off-center in relationship to each other when they clashed together. In all U.S. coin series, there are only 6 validated off-center clashes known; 3 on Indian cents, 2 on Two cent coinage, and 1 on Morgan Dollars. The main question for this type of variety is whether they were created in the coining press or during some other period in the die making process. There are several coins that were believed to be off-center clashed dies, but do not have the physical diagnostics to classify them as such. For example, there have been over 40 Morgan Dollar die varieties classified as off-center denticle clashing. For the 19 Morgan Dollars examined for this book, all but one of these has been refuted as an off-center clashed die.
Multi-denominational clashed dies occur when working dies of two different denominations strike each other without a planchet between. In all U.S. coin series there are only 6 known off-denominational clashes known; four of which occurred in 1857. One of the primary questions for this type of variety is whether they were intentionally made or simply the result of an accident. Another issue is how they could have occurred.