This is what is called a chopmark. As such coins circulated in China and other parts of Asia, these were stamped to see if they are actually silver instead of plated silver. Essentially this made it a "bullion".
My partial coin collection http://www.omnicoin.com/collection/gxseries
My numismatics articles and collection: http://www.gxseries.com/numis/numis_index.htm
Regularly updated at least once a month.
My numismatics articles and collection: http://www.gxseries.com/numis/numis_index.htm
Regularly updated at least once a month.

























