Odd spot on S4 T2 rotor (detonation?)
 

Thanks again for any help that you can provide. I am in the process of rebuilding the engine in my 10AE FC. The engine ran and made compression before it unfortunately sat for about 5 years. Currently, I am in the cleaning and inspection phase. After getting the carbon off of my rear rotor, I noticed this spot on the curved face.

https://cimg4.ibsrv.net/gimg/www.rx7...5ed7d6e530.jpg
https://cimg6.ibsrv.net/gimg/www.rx7...1fa039213f.jpg
My best guess is that this is from detonation but I'm not sure. It seems that every other picture I've seen of detonation damage on a rotor involved a dent located closer to the apex seals.

The most important question would be whether or not this renders this rotor unusable in my rebuild. Every other major component has been within the FSM specs so far. Thanks again for any help and advice with this question.

Ingested debris or manufacturing defect. Detonation in and of itself doesn't have that localized of an effect.

It appears to be right on the opposite side of one of the internal cast support ribs.
https://cimg1.ibsrv.net/gimg/www.rx7...8bcdb06af9.jpg
https://cimg3.ibsrv.net/gimg/www.rx7...d0e6e2bb68.jpg
I cleaned the carbon out of the indentation and it's maybe a half a mm deep. Would you think it's safe to continue using?

What does the housing looked like?

The housing appears normal. I don't see any obvious traces of that spot anywhere. The sliding surface is smooth to the touch.
https://cimg1.ibsrv.net/gimg/www.rx7...abab6f2cdd.jpg
https://cimg3.ibsrv.net/gimg/www.rx7...4540e41c20.jpg
https://cimg6.ibsrv.net/gimg/www.rx7...89795431df.jpg

I wouldn't have a problem using that rotor in a personal build.

looks fine to me yes, maybe slightly radius it with a shap carbide cutter if you be afraid it could start a crack during thermal cycling.