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Any Ideas on how to remove dust behind the cover glass. See on the left side. Thanks!
More likely you have screen persistence! Not dust Your system came with a sealed panel. This is where the cover glass is glued to the LCD panel as such dust really can’t get in. Update (12/06/2018) Sorry, you’ll need a new screen following this guide iMac Intel 27" EMC 2546 Display Replacement and here’s the needed part iMac 27" Display LCD Assembly, Late 2012 - Apple P/N 661-7169. You might want to alter your background image to be a more uniform image (a solid color)
