The neutral lugs in the meterbase look insulated, but from the size of the scortch-mark, maybe not?
Not would be a good guess. The neutral lug is the one in the center, where you see a green conductor terminated. (I have but rarely seen a meter can in which this terminal is insulated.) It's mighty nice of these DIYers to use proper color code so we can dissect their apparent intentions despite the scorch marks. Consider the insulated lug on the lower left to be a hot lug. (Neutral on the right lugs is the correct wiring for a 120V socket meter, but I digress. Such meters are not used nowadays.) Were it not for the PVC nipple, the meter installer would have been the one to see the arc, and it would have been even uglier than this!
