This is a title vignette from an edition, probably that of 1749 published by William Sandby, of the works of Horace.

The text 'Ex Num: In Thes: Christinae Reg: Aug:' is an abbreviated form of 'Ex Nummo In Thesauro Christinae Reginae Augustae', i.e. "From a coin in the collection of the august Queen Christina', probably a reference to Queen Christina of Sweden (reigned 1644 - 1654), a renowned collector and art patron.