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I don't know, 2 out of my last 3 iPhone 5 AC replacements came with iOS 6.1.X (one was .3, other was .4) both manufactured in Dec 2013. I updated to 7 shortly after receiving them. Going back to 6.1.X was weird.

Mine was replaced through the mail with Express Replacement. Verizon, White, 32GB.
 
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