That damage is from the coil laminations rubbing on the flywheel magnets. That happens when the coil wasn't installed correctly. The laminations are supposed to be flush with the machined edge below it.
Yours may work ok after adjusting, But the individual laminated plates are shorted together, compromising their efficiency. They are supposed to be insulated from each other to prevent eddy currents. There's something for you to do in your spare time---Google magnetic eddy currents and transformers.
