My blue painted 69 340 had no blue paint on the clamp. But the clamp was black with what I thought was some kind of black plating or paint. The black did not seem to be grease or dirt. Anyhow it cleaned up recently with mild scrubbing to be copper plated steel, which totally surprised me.

As the original owner, I never, ever saw copper plating, even though I worked on the points and timing every year or two in the 70s and early 80s.

If there was no engine paint on the clamp, should the clamp have been noticeably copper plated? Or could it have arrived from the factory with black copper oxide on the copper plating?

"Oxidizing (blackening, coloring) of a copper workpiece is commonly carried out by immersion of the part into a heated alkaline solution containing an oxidizing compound (e.g. sodium chlorite)." From:

http://www.substech.com/dokuwiki/doku.php?id=black_copper_oxide_coating