Like many recent CGC graded books, Newton Rings are visible with this case at certain angles. What follows is an explanation of this effect from CGC. The rainbow effect or Newton rings are a normal occurrence when two different plastics (which have different refractive indexes) are placed together.
Its what you sometimes see on a smartphone screen protector or on the edges of an LCD screen. The rainbow effect has been seen in CGC holders since our first-generation holder was introduced nearly 20 years ago.
This is a result of the inner sleeve (which holds the book) contacting the hard-plastic outer shell; the two different plastics have different refractive indexes and that sometimes creates a rainbow effect when they come into contact. A minor rainbow effect has always been within our tolerance. If anyone feels that they have a book that exhibits an extreme rainbow effect, however, we encourage you to contact our Customer Service at submissions at cgccomics dot com. The item "AMAZING SPIDER-MAN #300 CGC 9.4 1988 CLASSIC COVER 1ST VENOM WHITE PAGES" is in sale since Friday, August 30, 2019. This item is in the category "Collectibles\Comics\Copper Age (1984-1991)\Superhero\Spider-Man".The seller is "jokerswildcomics" and is located in Manhattan Beach, California. This item can be shipped to United States, Canada, United Kingdom, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Australia, Greece, Portugal, Cyprus, Slovenia, Japan, China, Sweden, South Korea, Indonesia, Taiwan, South africa, Thailand, Belgium, France, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Germany, Austria, Bahamas, Israel, Mexico, New Zealand, Singapore, Switzerland, Norway, Saudi arabia, Ukraine, United arab emirates, Qatar, Kuwait, Bahrain, Croatia, Malaysia, Brazil, Chile, Colombia, Costa rica, Panama, Trinidad and tobago, Guatemala, Honduras, Jamaica, Brunei darussalam, Ecuador, Jordan, Sri lanka, Luxembourg, Nicaragua, Peru, Paraguay, Viet nam, Uruguay.