This page from 'Liber sextus Decretalium' (The Sixth Books of Decretals) by Pope Boniface VIII (1294-1303). For centuries, the Sixth Book of Decretals was considered one of the chief texts of canon law. The University of Sydney Library holds both manuscript and print copies of this text. This is a printed copy from 1476.
As this book was printed before 1501, it is considered an early printed book. These are referred to as incunable or incunabulum, from the Latin "incunabula" meaning "cradle".
The decorations on this page (called "illuminations") would have been hand coloured. The term used to describe this type of illuminated letter B would be "historiated", as this initial contains an identifiable scene or figure.