Well, as it has become part of the discussion, I guess I'll briefly tell how I view the two images in question...assuming I can figure out how to get both images here side-by-each.
....And, I can't. So you'll just have to scroll up and review the images - sorry.
I'll refer to Pic #3 of Post #3 (aa), the head on the right vs. Post #6 (bb):
The hole in aa is more towards the middle of the head while in bb it is at the rear. Also in aa, the rear of the head "appears" (from the limited view) to come to an edge. Blunt, yes, but it looks to me as a vertical edge, sort of like a dull axe or splitting maul, only with a much shorter edge. In image bb, the rear is rounded and full height.
From what "I" see of aa, I'm not sure I'd classify it as an anvil - I'd need to do more research. It looks like a tool head with a point on one end and a short, dull edge on the other. Do ancient anvils look like this? I dunno. Do more modern sickle mower parts look like this? Again, I dunno. I've seen a few mowers up close but have never worked on one or operated one. Never really paid that much attention to them, to be honest. Almost bought one at an auction one time, but it sold for a LOT more than I was willing to go.