PCGS may refer to:

• Parallel communicating grammar systems, grammar systems working on their own string and communicating with other grammars in a system by sending their sequential forms on request.
• Preconditioned conjugate gradient square method, a variant of the preconditioned conjugate gradient method – an algorithm for the numerical solution of systems of linear equations whose matrix is symmetric and positive-definite.
• Professional Coin Grading Service, an authentication and grading service for rare coins started by seven coin dealers in 1985 to standardize coin grading.

This disambiguation page lists articles associated with the title PCGS.
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