I had a look through my X10 eye loop and I think it's just a scored line rather than a crack, I can see pitting in it. I wish my phone had a macro setting.
It does. But you have to push the macro button to see it like this. I think you're correct. That's doesn't look like a normal crack to me. I'd say throw it back in there and check it again in 50 years just to be sure. 8^)
I had three others look at it, one being the machinist I use for headwork. We all came to the conclusion that it is not a crack just score or imperfection in it. So it's in !