A monocle is a type of corrective lens used to correct or enhance the visual perception in only one eye. It consists of a circular lens placed in front of the eye and held in place by the eye socket itself. Often, to avoid losing the monocle, a string or wire is connected to the wearer’s clothing at one end and, at the other end, to either a hole in the lens or, more often, a wire ring around its circumference.
The antiquarian Philipp von Stosch wore a monocle in Rome in the 1720s, in order to closely examine engravings and antique engraved gems, but the monocle did not become an article of gentlemen’s apparel until the 19th century.
The dandy’s quizzing glass of the 1790s was an article of high fashion, which differs from the monocle in being held to one’s eye with a handle in a fashion similar to a lorgnette, rather than being held in place by the eye socket itself.
Here below is a photos collection that shows monocles in adverts and posters in the early 20th century.