Jagiellonians, Sigismund I the Old (1506-1548), half-penny 1517, Vilnius mint.
Grand Duchy of Lithuania, A very rare variant of the half-penny with a full date.
In the catalog "Lithuanian coins 1495-1536" by Huletski, Bagdonas this coin is listed under number H47A with rarity V (RRR or R5), where rarity I is unique and rarity X is a popular coin.
Silver, weight 1.20 grams, diameter 20 mm