Technical can a Chevy guru explain this intake?

that was exactly my first impression also-a C3B. It stood for carburetor 3 barrel-used on a lot of mopars in the day. Edlebrock produced them, but this one has the firing order on it and i didn't seen any mfg. name. They are still a good solid intake, i'd use it anytime (i have one on the shelf now, waiting). Chevy might have produced them from the factory, a good mystery.