1929 P LWC Incused Date, Motto And Epu. Chemical? Environmental?

The areas you see the devices recessed are the ones that normally collect the most gunk from circulation .
A too aggressive cleaning of a gunked up coin with acetone can often leave iridescent fields in just the areas where you see recessed devices on your coin. This effect is the grease protecting and toning these spots.
It's the protected original field that is defining this anomaly

Thanks for the update . It is damage , but rather cool damage!

I suspect it was black in color. Then it was cleaned to lighten it up. Almost reminds me of the way the copper/nickel cent looked when I cleaned it . The surface metal falls off and leaves the lines. On mine, it was even worse. The surface was showing no lines, just looked like it was chizelled away. What was the weight of this one? If it was strongly cleaned, it should be under in weight. But years ago, the common thing to do to preserve coin was to put lacquer or varnish on coins to preserve them. On the devices, it looks like this may have happened as you see a haze on the devices. Just looks like a coin that may have been ruined years ago and they tried to fix it making it worse.