The Collaborative International Dictionary
Duodecimo \Du*o*dec"i*mo\, n.; pl. Duodecimos. A book consisting of sheets each of which is folded into twelve leaves; hence, indicating, more or less definitely, a size of a book; -- usually written 12mo or 12[deg].
Wiktionary
n. (plural of duodecimo English)
Usage examples of "duodecimos".
But the story would include a chain of events extending over the better part of two centuries, and written out with reasonable amplitude, would fill a bigger folio volume, or a longer series of duodecimos, than could prudently be appropriated to the annals of all New England during a similar period.
Books were heaped on tables and under tables -- big folios, tiny duodecimos, every sort of book ranging from incunabula to what seemed to be a complete collection of first editions of Edgar Wallace.
Above Voltaire an even greater number of small octavos and duodecimos whose labels he could not distinguish: novels, in all likelihood.