I'm thinking die gouges or maybe a strike through. That area would be a high point on the die face the o and the edge lower.
It would take a pretty careful hand to do that after the strike and not put a scrape on the edge or the o and just in between them. It's also not a crack, it would also be visible on the rim if it were.
I'd say it's two small die gouges on the die face as most likely, And doesn't appear as if it would be likely to have happened post strike while waiting to go into the set because it surely would of affected the rim or the o.