a housing comprising a first surface oriented in a first direction, a second surface oriented in a second direction opposite to the first direction, and a side surface at least partially surrounding a space between the first surface and the second surface;

a base ring located adjacent to an edge area of the first surface and rotatably mounted on the housing;

at least one first magnet disposed on the base ring;

a first ornamental ring detachably mounted on the base ring and configured to rotate relative to the housing together with the base ring;

at least one second magnet disposed on the first ornamental ring and configured to generate an attractive force with the first magnet; and

an interference member configured to perform a linearly reciprocating motion between a first position and a second position closer to the second surface than the first position, the interference member being located adjacent to the base ring and the first ornamental ring,

wherein, at a position where the first magnet and the second magnet face each other, the first ornamental ring is mounted on the base ring, and

wherein at the second position, the interference member is configured to maintain or fix the base ring in a stationary state relative to the housing by being at least in partial contact with the base ring and the first ornamental ring rotates relative to the base ring such that the second magnet leaves the position where the second magnet faces the first magnet.