Ron Guth:
Proof 1879 Half Dollars are very popular with collectors because of the tiny mintage of circulation strikes (4,400 coins) in the same year. This puts tremendous price pressure on this date from collectors who seek any 1879 Half Dollar -- in this case, the Proofs are more common than Mint State examples. Thankfully, hundreds of Proof 1879 Half Dollars exist in a range of grades from PR60 to PR64. Even PR65 and PR66 examples can be found with relative ease. Only in PR67 does this date become a condition-rarity. Only 15% of the total population of Proof 1879 Half Dollars are considered Cameos. As is typical of the dates of this period, the 1879 Half Dollar is extremely rare as a Deep Cameo.