Post #6 -- I get a Jabo feeling from these.
Jabo is a Reno, Ohio company who started making toy marbles in 1991. (Industrial marble before that)
Post #7 -- This plate might have a mix of older and newer. I think I may see at least one West Virginia swirl, which would be older. And there might be an Akro, which would be older. More views could help there.
Post #8 -- I think Jabo again on these.
Post #10 -- modern Chinese as popculturizm said