A "chop mark" is a Chinese character or characters stamped into a coin by a merchant who is essentially validating the weight, authenticity, and value of a given coin. This facilitated the circulation of silver coins in the Orient, which was the intended market for U.S. Trade Dollars. Chop marks vary in size and shape, and a particular coin may show only one chop mark or it may be chop marked so often and so severely as to be almost mutilated. PCGS certifies chop-marked Trade Dollars because of the frequency with which they occur and because of high demand from collectors. One of the more challenging sets in the PCGS Set Registry is that for chop-marked Trade Dollars, which requires collectors to asemble a complete date and mintmark set of Trade Dollars - all with at least one chopmark!
The 1874-CC is among the more common of the chop-marked Trade Dollars, and it also has one of the highest rankings in the Condition Census, with two examples at the MS64 level (see the illustrated coin above).