The 50 Cent Piece is rarely used, but mostly used in Casino's. Half Dollars had been made since the 1790's and John F. Kennedy is on the coin (Designed by Gilroy Roberts). here are some facts about this coin:
Mass:11.340 g. 30.61 mm (1.205 in)
Thickness: 2.15 mm (0.085 in)
Edge:150 reeds
Composition:91.67% Cu 8.33% Ni