Kiratamurti or Kiratarjunamurti is a form of Siva and he appeared in this form in response to Arjuna’s (One of the Pandava brothers from Indian epic Mahabharata) penance.
Arjuna undertook the penance to earn Pasupata, a weapon whose deity is Siva. In addition, Arjuna had to prove his worthiness by combating Siva, who appeared before Arjuna in disguise. When Arjuna realized that he is combating someone superior to him he started worshipping a Linga, aniconic form of Siva. Then Siva appeared before Arjuna to present him the weapon, Pasupata.
What we see here is a depiction of Siva’s appearance with Pasupata, Bow and arrow on his left hand, the weapon that Arjuna coveted. See the profile for a view of the arrow.
The halo around the head signifies it is a deity. One of the identifying features, of Kirathamurthi, is the long sword on his right hip and Siva’s right hand resting on the sword’s handle. The idol is standing on a squarish pedestal devoid of any patters. Such pedestals are not uncommon among Kerala bronzes.
The idol is about 14 cm is high. It is from Kerala. One of the unusual features is the total absence of incision/chiselling in the working. The ornaments are embellished on the cast portion as compared to idols from the neighbouring regions (Andhra, Tamil Nadu and Karnataka) where the cast images are incised or chiselled to detail the ornaments. This idol may date prior to the nineteenth century.
There is a similar but larger example in VAM. Try http://collections.vam.ac.uk/item/O62826/sculpture-figure-unknown/
This blog site has another example that may be Kiratarjunamurthi.