I can tell that they're different, but the differences are really subtle in large groups of them. Numbered left to right, top to bottom. 2,4,6,7,9 look close

I can tell that they're different, but the differences are really subtle in large groups of them. Numbered left to right, top to bottom. 2,4,6,7,9 look close enough that I probably wouldn't be able to guess which one it was if I only saw one of them at a time. 1,3,11,12 looks similar, I might be able to tell the recognize 3 and 11 on their own. 10 looks similar to the 2nd group, but is different enough that I could probably pick it out. 5 and 8 are unique enough that they stand out by themselves.