This coin could be "Struck Through Grease", But I would sooner think it a incomplete or "Weak Strike" due to the fact it has so much missing design on both sides. A "STG" usually [out on limb here] will only effect one side,and in a smaller area. Your coin seems to have a strong rim which can rule out a "Squeeze Job" from a vice or such. I don't think it's PMD. So I'm going with "Weak Strike" .