I'd clarify - there's a distinction between "oldest observed" and "oldest we think are possible" and the known in this context (for me at least) leans strongly

I'd clarify - there's a distinction between "oldest observed" and "oldest we think are possible" and the known in this context (for me at least) leans strongly into the "oldest observed" camp for me - though, as with all things english, technically it could mean anything.