The 1877-S Quarter Dollar is a common date and has one of the largest mintages in the series. Hundreds of Mint State examples have been certified, and many more exist in a raw state. The most common Mint State grade is MS64. Dozens exist in MS65 to MS66 grades, but any example in MS67 is an extreme condition-rarity.
With so many examples to choose from, collectors have the opportunity to be picky. Look for fully struck examples with clean surfaces and above-average eye appeal.