If it helps, this pair of problematic POPs for cards that don't exist immediately comes to mind...
There is no card #603 in the 1961 set. The 1971 Topps Pirates Team is card #603, so they most likely mixed up the 6 and 7 of the year during the grading process:
ScreenShot1961piratesteamwrongpop.jpg
All 1962 #139 Hal Reniff portrait variations are the 'regular' versions, not the green tints, yet the POP report lists 4 of them:
ScreenShot1962reniffportraitGT.jpg