With the second largest mintage of the entire Seated Liberty Half Dollar series, the 1877 is, simply put, common. PCGS has certified over 200 examples of this date, most of which fall into the MS62 to MS64 range. Even Gems are relatively common, with a varied selection of nice coins awaiting collectors in MS65 and MS66. In MS67, this date becomes incredibly rare.
The strike quality on 1877 Half Dollars is usually quite good, but keep an eye on the stars on the right side of the obverse - sometimes they can be a trifle weak.