340-6 Intake manifold part numbers. Original?

I have two 340 six pack intakes. One has part number 3418682 and also says LD6B. The second has part number 3418681 but no LD6B. I think the 681 could be an original but not sure. Any way to tell?

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Looks like the one on the left is the original one....the one on the right is not.