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PerryHall

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Posts posted by PerryHall

  1. Several years ago Coin World did extensive tests on the slabs of the major grading servicesfor a detailed article and found that none were totally airtight although the NGC slabs came closest to being airtight. Remember that when the barometric pressure rises, air will enter the slab and when the barometric pressure drops, air will leave the slab resultingin a constant change of the air in your slab. Also, if a coin were dipped and improperly rinsed prior to slabbing, the residual dip on the coin's surface will cause the coin to discolor over time even though it's housed in a slab.