Unknown Countermark.

Hi, this is a pre-1866 Austro-Hungarian silver hallmark, usually applied by a silversmith or jeweler to certify purity (in this case, indicating 13/16 parts silver, or .813AR). Though such hallmarks were applied in the Balkan border regions of the Empire, I have only ever seen them on Turkish coins. Also, the date on this punch appears to be 1806 - peculiar, as the mark far predates the coin, and indicates a lower content than the actual purity of the specimen in question (.835AR). My best guess is that someone in the Balkans border region got hold of an old punch, and was using it to "self validate" coins for local circulation, with the Imperial hallmark allowing for more ready acceptance of imported coin. Hope this helps! -A.