I don't see any signs of age whatsoever. How did you clean it? Way too clean, but if you know it's good this is beauty actually worth a COA.
Flint/chert artifacts found in a large-lake or ocean shoreline context usually don't show any patina, if anything they often look somewhat polished if not worn away to the point of difficult to identify depending on sand type, sand content, and wave action.
In creeks and rivers where there's a high concentration of tannic acid from trees and other minerals in the soil patina will be more likely or expected.
What would be a reason to get an COA and how would I go about that? I am not knowledgeable on these.
If it is authentic what would be the going rate? I mainly keep my finds though
Very nice! Keep hitting that area!