The flaw was definitely inside. I kind of take exception to the word "modified" as applied to sharpening and hand-polishing the surface. Technically, it IS modified from the factory condition, but any sharpening would do that. I really didn't remove much in the way of surface metal, if you can imagine removing a significant amount of THIS steel by hand!!
The thing that most impressed me was the dead-center placement of the flaw, and the way it looked like the edge peeled in half. Like the stock was rolled or folded from 2 pieces. i wish I knew a little more about foundry processes.
Along time ago I made a couple of swords for my 12 year old cousins to hang on there walls. I picked up some 1/4"x 2" 5160 new bar stock. I roughed it out and took it back to the spring shop where I bought it to have it heat treated. Brought it home and started to polish it and OMG <img src="/ubbthreads/images/graemlins/ooo.gif" alt="" /> <img src="/ubbthreads/images/graemlins/ooo.gif" alt="" /> <img src="/ubbthreads/images/graemlins/ooo.gif" alt="" /> there was a line about 1/2 inch in from the edge running the entire length. A closer look revealed it was a seam and could not be polished out <img src="/ubbthreads/images/graemlins/frown.gif" alt="" />.
Well I finished the polish and blued the blades to hide the flaw. Apparently it's not uncommon during the milling process for the metal billet to have folds usualy near the end. In a wall hanger it's no big deal but a user <img src="/ubbthreads/images/graemlins/ooo.gif" alt="" /> Not good.