A plus or concave mirror adds positive vergence, to aid the act of shaving for instance. By the mid eighteenth century, facial hair fell dramatically from favour as the face of the polite gentleman was increasingly clean-shaven. The arrival of the newly-invented cast steel enabled razor-makers to produce ever sharper (and indeed blemish-free) blades, rendering shaving more comfortable, and razors more durable and capable of re-sharpening. Shaving the face evinced neatness and elegance, and notionally separated the gentleman from the unkempt yokel whilst shaving the head prepared it for the wearing of a wig – an expression of gentlemanliness, masculinity and taste.
A decidedly rare and acutely original Georgian relic.