From Wikipedia:
The plaques themselves contain various items under the glass. Modern awards often use CDs instead of records. Most gold and platinum records are actually vinyl records dipped (or otherwise coated) in fine metallic paint, while trimmed and plated metal "masters", "mothers", or "stampers" (metal parts used for pressing records out of vinyl) were initially used. Rarely does the groove on the record match the actual recording being awarded. Individual plaque-makers produced their awards according to available materials and individual techniques employed by their graphic arts departments. The plaques, depending on size and elaborateness of design, cost anywhere between US$135 and $275, most often ordered and purchased by the record label that issued the original recording.
