Ron Guth:
Proof 1859 Quarter Dollars are fairly common, though that is a relative term since a mintage of approximately 800 pieces is very small to begin with. However, in the arena of numismatics, if a collector wants a Proof 1859 Quarter Dollar, he/she can find one with relative ease. The vast majority of Proof 1859 Quarter Dollars are non-Cameos. Approximately 10 percent are Cameos, though that percentage may be as high as 20 percent. Deep Cameo 1859 Quarter Dollars are exceedingly rare.
PR63 and PR64 are the most frequently seen grades. Any examples in PR66 or better are very rare, and the best examples top out at PR67.