Since its introduction in 1986 by the Professional Coin
Grading Service (PCGS), slabbing--the encapsulation of coins
in sonically sealed, hard plastic holders--has greatly
diminished the grading controversy that plagued the market
prior to that time. It also has eased the crisis of
confidence that up to then was spreading insidiously through
the marketplace. Today, there is widespread acceptance of the
grades assigned to rare coins by PCGS and other leading
certification services--notably the Numismatic Guaranty
Corporation of America (NGC) and ANACS.

Interesting article about the myths of slabbing, click the link below to read.

Dave.
SS - 1029