yes my books don't show that shape, however it does state that square plates were made. It does feel sharp, especially on the bottom.
Also the tips don't flare out like english hobnail, and the rays are equi distant. But I still am unsure. I have not been to replacements yet, but I have found errors there, so not always full proof.
I was hoping someone had a picture or a thread of square miss america plates, or has seen this pattern and knows it. The crimped edges is what has me unsure.