Smoke damage maybe, heat, not so sure since the front clear panel and inner panels aren't melted or distorted.
Looks to me like a unit that lost its metal cover, sat outside in a shed. The corrosion and general filth inside the chassis looks formidable. I would be especially concerned about the tuner sections and the variable capacitor and how well they would clean up. It is an international voltage unit though.
As for the front panel, looks like maybe someone went amok with a sharpie pen coloring things black. IIRC that would come off with Mr. Clean Magic Eraser or denatured alcohol. I dunno, cosmetically, I don't think it would be hard to clean up, knob costs aside. But operationally, a lot more work.
Nice receiver in general though. Hmm, located in California, maybe a local pickup for some to prevent further shipping damage?