The 7-finned aluminium valve covers (we call them 'rocker covers' here in Australia btw) used on high performance Corvettes first appeared in 1956. At some point (the exact date is disputed, some say mid-'65, others say '66) a crack in the tooling introduced a casting flaw — a line running through the 'o' in Corvette (visible in the images below).
As the Red Rocket is an early '65 car, its original valve covers did not have the casting flaw. Unfortunately a previous owner cracked one of the original covers by over-tightening it (an easy mistake to make, they're very fragile). The remaining cover is still on the car, the cracked one is with the car but unusable.
The guilty owner purchased a pair of 'GM quality' replacement covers from Zip Corvette. They are a licensed GM Restoration Part (made by Paragon using what's left of the original tooling apparently), and they include the casting flaw. In addition to this flaw, these valve covers have a LOT of other flaws, and the aluminium is very uneven in colour and texture. Out of the box they look awful, be prepared to do a lot of hand finishing if you want them to look any good on the car.
I spent a stupid amount of time sanding the cover to remove the casting flaws — including the line through the 'o'. That flaw is quite a deep crack, but it was possible to almost completely remove it using a Dremel and lot's of wet-and-dry.
Once I had finished sanding the flaws out I sent both the new valve cover and my original, flaw-free one over to Sydney Vapour Blasting (link below).
Vapour blasting is perfect for restoring aluminum parts. It's non-destructive, and produces a finish that looks almost like the piece has been painted. The result was very good, the blasting gave both the covers an identical finish, it's impossible to tell that they were cast 5 decades apart.
The finishing touch was to apply a new set of '350 Horsepower' water-slide decals from Corvette Central that perfectly match the originals.