I agree, a silver karshapana of the Mauryan Empire. The standard reference for the series is by Gupta & Hardaker who catalogued more than 600 symbol combinations. Generally, each coin has 5 symbols on the obverse and one on the reverse, often accompanied by secondary banker's marks. In the 1970s, Mitchiner attempted to attribute various symbol sets to specific rulers but his work has not been widely accepted. Gupta and Hardaker have arranged the coins into a rough chronological series based on hoard evidence. The full date range is c. 321-150 BC. Unfortunately, the symbols on this example are not clear enough to identify.