This bronze Vigraha is Trimurthi, with a single head, six arms, a single body and two legs. Trimurti is a syncretic form of Brahma, Siva and Vishnu (in alphabetical order).
Brahma, Vishnu and Shiva, as per Hindu beliefs, are responsible for creation, protection and destruction respectively. It is not unusual for them to be depicted on the same platform as three independent deities. Syncretic form, similar to the one here, is less common.
Stone sculptures of Trimurthi are not uncommon in South India. There is a view the syncretic form was conceptualized to counter sectorial thinking. However, there are Saiva and Vaishnava renderings of Trimurthi!
Trimurti’s hands are holding /in Vykhana Mudra (preaching mode), Trishul, Chakra (discuss), Shankha (conch shell), Elephant Goad and Kamandala (water pot). Starting from the lower right hand clockwise. Vyakhana Mudra and Kamandala are Brahma’s attributes, Trishul and elephant goad are Siva’s attributes and Chakra and Shankha are Vishnu’s attributes.
This website has another Trimurthi fashioned as an arm-band.
Features to note include that mysterious smile and the pronounced stomach. The Vigraha is not sharp, but this does not appear to be a sand-casting.
This Vigraha is about 13.5 cm in height. The alloy is copper-rich. There is significant wear and it suggests a date of the nineteenth century or earlier. This is, most likely, from the Karnataka region.
Note 1: The iconography of Dattatreya and Trimurti overlap to an extent, single heads, six arms with the attributes of Brahma, Siva and Vishnu, single body with one pair of legs. The differences are normally in the Vahanas and footwear: Dattatreya is accompanied by dogs and cows and Dattatreya wears Paduka (footwear). The absence of footwear, a very important cognizance for Dattatreya, suggests this is Trimurthi.
Note 2: There are other iconographies of Trimurti for example, Ekpada (one leg) Trimurti where they are depicted with a single leg and three torso/heads.