It doesn't look like detonation to me. Detonation looks like sandblasting with coarse sand. The only thing I see is some hammering, from some kind of object. A piece of ring or piece of spark plug.
Below is a picture of a head with detonation. Its difficult to see on the photo but some material is actually missing. Its been corroded away by the explosions. In the marked area there is a groove as if it was etched out by acid.


_________________
Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom