This six-armed Vigraha is identified as Manjushri on the basis of the sword and hand mudra. With three heads (The head on the left is discernible) and six arms, it is an esoteric manifestation of bodhisattva Manjushri.
The six-armed versions I have come across are with the front hands crossed, signifying Vajra mudra or holding of his consort, Prajna. Here the hands are in Dharma Chakra mudra. So far I have not seen any reference to this form.
The sword signifies Manjushri cutting through ignorance.
Two-armed Manjushri is more common. This website has an example of a two-armed one.
The Vigraha is about 5 cm in height. It is from Bihar/Bengal region. It is quite likely this may be dated to the late Pala period, the 11th-12th century.
Reference: The Indian Buddhist Iconography 1968 Benoytosh Bhattacharya.