My first thought was the same a John, cut down sign. Especially since there are no mounting holes along the top. But if its a porcelain sign a cut along the top should be very obvious, and I agree with you, I dont know any signs with the "time tells" on the bottom anyway.
Maybe whomever was making these signs in "ye olde times" used the round blanks, cut it down, and put on these different graphics. You would have thought they'd flange it though. Strange.
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