Although James Searle labeled it a cipher, this document is in fact a code. In a code, each code word has one specific counterpart in the plaintext. In the code used by Adams, Dana, and Searle, for example, “D.D.” always means Benjamin Franklin. In a cipher, however, letters or numbers are transposed or substituted according to a predetermined key.

Francis Dana and John Adams employed the code in letters exchanged between January and April 1781. The code likely originated with C. W. F. Dumas, who used the code word for Congress, “AZ,” as early as 1779, and Dana and Searle revised it to serve their needs (Weber, Codes and Ciphers , p. 63–64). The code names, at least in some cases, clearly describe individuals and institutions, or at least how they were perceived by those who devised the code. Some, such as “Steady” for John Adams, ring true. Others, such as “Grex”—Latin for herd—to describe the States General or “Nestor” an aged, wise advisor—to denote Dumas may be less evident to today's reader.