Hey guys, sorry I didn't get a very good picture of this, but I saw this skillet today. The bottom is pretty crusty and the only mark you can see is a diamond in the middle with what looks like a T in it. (It obvious somebody else was wondering too and sanded around it for a better look.)
https://imgur.com/a/vMjzU
It doesn't appear to have a heat ring, but that could be buried under the crust.
https://imgur.com/a/vMjzU
It doesn't appear to have a heat ring, but that could be buried under the crust.