The stubby idea is a good one but the crack is about a 1/2 inch from stabilizer.. it's kind of a u shape thatstarts at the edge goes up a 1/8th and back down like a chunk is about to come off.. I don't know..

Btw, I dont think this was ever a 5/8 or even 4/8. That was my initial thought as well. The shoulder is different than any other wostenholm I've ever seen. On all the others I've seen, the stabilizer clearly comes down towards the edge but this one has no stabilizer at all, and was undercut past where it would be. That being said, I've never seen a one this small that was a near wedge before either so, who knows.. mute point now, but still interesting to me.