How to tell a Scratch from a Crack in a Cylinder?

Here's That Piston (Untouched, as it came out)
and the Line as seen from the top...
It's 3 1/2" down from the top So, it's Under the Rings.
I didn't do that Honing it... It had a (Very Bad) Previous Rebuild. Sorta. The Ring Gaps were All Waaay Too Big and it Smoked, Alot.

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I'd probably replace those pistons if it was me.