Matching sleeve size to your cards helps avoid shifting, crowding, or pressure
After extensive research by CGC, including conducting an infrared test, UV test, and X-ray fluorescence (XRF) spectrometer test, all of the chemical elements, most notably calcium, titanium, iron, copper and zinc, all correspond with a normal 1999 Base Set card
Back: All four corners are visible and look sharp with no significant rounding or wear
And the card backs are notoriously difficult to keep in mint condition, with corner whitening and surface imperfections being the most frequent issues that prevent otherwise clean cards from achieving top grades
I assume there must have been some way to test the cards and how they play out, despite it being undoubtedly more controlled than with MTG where R