Professional Coin Grading Service, an authentication and grading service for rare coins started by seven coin dealers in 1985 to standardize coin grading.
In the May 26, 2003 edition of Coin World, the hobby newspaper had announced they had contracted investigators to conduct a year-long, comparative study of PCGS, ACCGS, NGC (Numismatic Guaranty Corporation) and several other grading services, each known as a Third Party Grader (TPG).
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