Still need an answer if anyone knows about the cover and if that is the old washer stuck inside.
mine was a copper washer (gasket) that was under the bolt head. The washer (gasket) should just pop off. It's copper colored if I remember correctly. It shouldn't be stuck to anything. I bought a new one and replaced when I did my stator.
it appears your cover is black. maybe somebody painted the washer to your cover