Sorry I couldn't quite work out how to explain it that well the first time. For the cross eyed test when you have that 'middle card' locked in, look all over the card. Anything that is solid is symmetrical and anything that looks to be half there isn't. Half there would be like how if you put your finger in front of your eye and look at something else your finger looks to be there but is also see through. You may need to be in a well lit area to see some of the differences when doing this comparison.
For Propagandas I know the dots around the side stars are one way, the side fin line on the bombs are one way, the blades or whatever it is in the center are one way, the 'shading' behind the grenades. Theres probably smaller stuff too. None of it is blatantly obvious though. I'm not sure about circle backs I haven't really looked at them.
FWIW If you have a sharpie to match the color of your deck you can make any deck one way...