I just came accross a set of Z28 aluminum dripless valve covers at flea market I paid 40.00 they appear to have a black coating its not paint any info. out there Marc/M&Ms Camaros

could be black anodizing

3932418 is the casting # on inside. Cast natural aluminum, dull smooth finish. If they are in good shape, $40 is a deal.

Sounds like they are off a late 70s L-82. They are a carry on of the old LT-1s from the early 70s. (And possibly 69 Zs) Mine came off a 70 model and had cast drippers in them. Unfortunately, I ground some on the drippers to work with roller rockers.
Virgil