Walter Breen's Encyclopedia of Early United States Cents

Clapp derived enough die state information from coins owned by himself, Newcomb, and Hines, to assemble an emission sequence then thought to be definitive. Sheldon copied it, renaming Clapp's obverses 2, 3, 4 as "2, 2VD and 2VD." New evidence (die states and planchet types) has forced major changes from the Clapp and Sheldon order. The more we learn about the chronological sequence, the less familiar it begins to look. Clapp's six types were not struck in their logical sequence; dies did not go to press in order of manufacture.

As in 1797, part of the difficulty in constructing an emission sequence consistent with the evidence is that some varieties consist of individual die pairs, while others come in discrete die-linked groups. It is not always clear which group followed which. Where die linkage is missing, punch linkage and planchet types provide necessary additional evidence; and some of this evidence is strong enough to force changes in the Clapp-Sheldon sequence. The EAC sequence, worked out by Denis Loring and myself, takes into consideration all such evidence then known; the present sequence is a slightly updated version.

Because the chronological sequence no longer follows the familiar Clapp types, you will do well to use the Cherrypicker's Guides and Key first. But be sure to verify your attribution with the main text. Some of the key points are inevitably similar to those used in Dr. Philip Ralls's attribution key, (Penny-Wise, no. 104,9/15/1984, P: 283.) though he and I devised ours independently.