The seller has said:
"I removed this nut and I cleaned it from strong "dirt". It looked like a crack on the photo really. "
I also asked about the reversed cable tensioner bolts in the later photos, he said:
"because of safe shipping. Like this do not drop from the arm. For you necessary to insert the adjuster screws in a good position into the holes."
Sounds plausible, I said to go ahead and ship, will have to see what I get...