quarter calf, morocco, etc.
Quarter bindings are those in which only the backstrip is leather; the sides are covered with a different and cheaper material, usually cloth or paper. May also be expressed as e.g. calf-backed boards.
The size of a book, or of the page of a book, produced by a standard printing sheet being folded twice to form a section of four leaves, or eight pages: widely abbreviated 4to. Hence also a book or volume of this size. As the size of a standard printing sheet has varied greatly over the centuries, the size of a quarto varies accordingly.