It is of interest for the image engraved on its surface. Traditionally interpreted as the 'Judgement of Paris', a closer look at the imagery makes me question that interpretation, but I'm at a loss as to what another interpretation might be.
The story of the 'Judgement of Paris' is a well known one. It occurs at the wedding feast of Peleus and Thetis (the parents of Achilles), to which all of the Olympian deities had been invited except Eris, Goddess of Discord. True to her name, to gain revenge she cast a golden apple into the crowd addressed 'to the fairest'. This of course caused havoc among the assembled deities, with Hera, Aphrodite and Athena all claiming the apple and the title that came with it.
Zeus was asked to mediate and, in a somewhat cowardly move, delegated the impossible task to Paris, prince of Troy. Each of the goddesses appeared before Paris, who was tending sheep at the time, and offered him a bribe in return for naming her the victor. Hera promised him an empire, while Athena offered him victory in battle and supreme wisdom. Aphrodite's bribe was to give him the most beautiful woman in the world, and it was this promise that swayed Paris to proclaim Aphrodite the winner. Of course, the woman in question was Helen, wife of Menelaos, and Paris' subsequent abduction of her ended rather badly for Troy.
The famous scene of judgement, with each of the goddesses standing before Paris, has been depicted in art many times, and has been an extremely popular subject with painters from the Renaissance to the modern day.
The classic depiction is as seen on the Athenian jar below, in the collections of the British Museum and dating to c.470BC. In it, Paris is seated on the right and the three Goddesses line up to offer him their bribes. Nearest to him is Hera, then Athena, and finally a veiled and modest-looking Aphrodite. Each goddess is identifiable via their attributes.
So what is the image on our mirror, and how does it differ from this typical depiction? Here is the mirror with the image outlined.
The medium - engraving onto bronze - means that a certain amount of subtlety in the design is lost, but the four figures are clearly shown. The central figure is female, and has a small amount of drapery wrapped around her legs. To the right is a seated male figure, naked apart from a Phrygian cap. The the left are two more figures, one seated and one standing with only head visible. The seated figure appears to be male and both wear the same Phrygian caps as the figure on the right.
The Phrygian cap is often associated with Paris, but he is more usually depicted as a shepherd, with animals beside him, and wearing a baggy tunic and trousers.
So what scene do we actually have here? Three males with Phrygian caps surrounding and all paying attention to the central female figure. She has her body turned towards the right hand seated figure, but her head turned towards the two left hand figures.
Is this a version of the Judgement of Paris after all? If so who are the other two figures in place of Aphrodite and Athena? Or is this actually a representation of a completely different mythological episode - if so, all suggestions gratefully received!