As you may already know, the very first batches of the Canon 5D Mark III had a manufacturing defect, where light would leak through the top LCD panel as shown in this and this videos. After a thorough investigation, Canon confirmed that the camera indeed had a problem, so it issued an official statement that it would fix the issue if you send the camera to Canon (free of charge).
Folks at LensRentals.com had a chance to disassemble both an original and a “fixed” Canon 5D Mark III and they discovered that Canon used a black tape over the camera components, which essentially takes care of the problem completely. Here is a picture of the black tape covering the components:













