Natural cast iron main body with brighter machined surfaces. Nice fresh new bare metal cover. Believe the plug at the end was zinc plated. I use darkened cover retaining bolts.
Only question is did 70 Dearborn black out the top (messy black lacquer applied with a big brush producing runs of paint down the sides, that year, plant and time period. Currently I don't think judging requires it but talking about originally. Let me see if I have any pictures that show