It looks like something has been chomping away at the inner edge, or is that just a layer of 'crud' stuck to the underside??
I have one sort of like that. The guy I got it from said it went in the ultrasonic painted side down.
Yikes, that original listing looks like it was left in soda for several months and slowly started dissolving.
I've taken a closer look and it's fairly obvious that the rough inner edge is not the bezel/insert, but is a build up of dirt or glue adhered to the underside of the bezel. While it may be the case that it has been chemically treated this bezel (and oddboy's) are less affected on the inside, close to the crystal, so they must have been treated while still on a watch. It would appear that the raised profile of the crystal protected the inner part of the bezel from contact with whatever medium (swab or sponge) was used to apply the 'bleach'.