This is Dakshinamoorthy, a form of Siva. He is the teacher of Yoga, Music, Dance and other sciences. He is holding Akshamala, Ankusha, Cobra and Pustaka in his hands, clockwise starting from the lower right hand. His right hand is in cin mudra, espousing wisdom.
Siva’s right leg is pendent and the left rests on right thigh. This is Virasana. Here Dakshinamurthy is sitting on a mound of rocks, depicts the Himalayas, and under a Banyan tree.
The right leg rests on Apasamarapurusha. Conquering ignorance (Apasmara) and espousing wisdom at one go. See the picture below for a better view of Apasmara. The two disciples, Rishis, have their hands in Anjali mudra. It is not unusual to see up to seven rishis shown in Dakshinamurthy sculptures.
Most of the Saiva and Vaishnava temples in South India will have Dakshinamurthy on the South wall.
This is most likely from Karnataka (based on the construction technique and the top knot of Siva). It is about 13.5 cm in height. The auction house had dated it to the nineteenth century and I am good with it. The sculpture is a three-piece construction, see the picture at the bottom.