This is Vishnu is seated position. It is a miniature version and is 5.6 cm in height. The detailing is visible despite the size and physical condition.
Vishnu’s hand hold Shankha, the Padma, Gada (Top broke?) and Chakra (Conch, Lotus, Mace and Discuss/Wheel), starting from lower right hand clockwise. Vishnu is sitting in Padmasana and on double lotus pedestal. The ornamentation is complete. The crown is quite tall, about 0.8 cm compared to whole figures height of 5.6 cm. Back is worked on and Yajnopavitha (Sacred thread) and waist chain details are showing despite the age and condition.
There are three types of Vishnu images standing (Sthanaka), seated (Asana) and recumbent (Sayana). The latter two are rarer. Now, this website has examples of all three.
The double lotus pedestal, beaded rim as the base and holding of all four attributes suggest the bronze is from Eastern India. The physical condition suggests burial in the ground for long period.
There is a suggestion that this form may be yoga variety of Vishnu as compared to the more common regal aspects.
H Krishna Sastri in his classic South Indian Images of Gods and Goddesses documents (text on page 55 and figure 37) Yogesvara Vishnu, with four arms and seated in a meditative posture and seated on a lotus. The bronze image above has legs in the yoga position and the hands are not in Dhyana mudra. Normally the seated Vishnu is in Lalitasana with his right leg pendant.
Pratapaditya Pal’s book The Elegant Image (Bhansali Collection) has a similar Vishnu bronze (page 72, catalogue no 34, height 6.9 cm). That bronze is dated to Pala period, 11th century.