This quiz was updated to exclude flags which matched the dimensions of any other flag. Previously, if there were only 2 flags total that had the same dimension ratio, I branded them as "Unique" due to their rarity, however I have since changed it to be truely unique and one of a kind. The pairs of flags that were removed in this latest update are Switzerland and Vatican City (1:1), Israel and Norway (8:11), Albania and Kosovo (5:7), Andorra and Brazil (7:10), and Iran and Mexico (4:7).
Also, I used the notation of "non-quadrilateral" rather than the dimensions of the total width and height as I feel it better represents the shape of the flag and its 5 uniquely sized edges. Conveniently, this also makes the quiz look a lot better as the ratio, should I have notated by total height and width, would have been 1:((6136891429688 - 306253616715(sqrt(2)) - (sqrt(118 - 48(sqrt(2)))(934861968 + 20332617192(sqrt(2))))/4506606337686) -- Obviously not a quiz suitable notation.