Ron Guth:
Workers at the Philadelphia Mint produced 600 Proof Half Dollars in 1868. A large majority (if not all) were sold, and most survive today. This date is slightly more common than 1867 and slighty less common that the 1870 and 1871 Proof Half Dollars, However, any coin with a mintage of only 600 is a desirable rarity. The overall quality of this date is slightly lower than normal, with the largest concentration of grades at the PR63 level. Gems can be difficult to obtain and anything PR66 or better is a condition-rarity. Cameo examples represent approximately one-seventh of the total population. Deep Cameos are exceedingly rare and may not exist at all.