This eight-armed Vigraha is Tryambaka, a form of Siva, and he is seated in Vajraparyanka. The dhyana of Tryambaka as in the Sarada-tilaka Tantra reads as follows
“He is seated on a lotus of transparent whiteness. He is beautiful like Mount Kailasa. He has three eyes. On his diadem is the digit of the moon. With two of his hands, he is bathing his head with nectar out of two jars held in two other hands. In two of his other hands are held a deer and a rosary. On two hands resting on the body are placed two jars. “
This vigraha matches the above Dhyanic prescriptions except for the lowermost hands. In this case, he holds a single vessel in front of the chest with both the hands. However, the Vigraha matches the example T E Donaldson has given in the book Siva-Parvati and allied Images Volume II Figure 455. See the photo. That example is in the sanctum of the thirteenth century Visvanatha temple at Krishnaprasad (Puri District), Orissa.
Tryambaka is also known as Mrityunjaya, the conqueror of death. The main iconographic feature of this Vigraha is the several jars of the ambrosia he holds and with which he bathes himself. As the ambrosia is a symbol of immortality, he is Mrituynjay, the conqueror of Death.
This vigraha is about 9 cm in height. Going by the above example from T E Donaldson’s book, this vigraha is from Orissa. This vigraha possibly dates prior to the sixteenth century.
There are other iconographic prescriptions for Tryambaka and Mrityunjaya (refer: T A G Rao’s Elements of Hindu Iconography).
Note: This blog borrows heavily from T E Donaldson’s book, referred above, and the book Hindu Religion and Iconology by Dr Pratapaditya Pal.