Do you have American Machine-Made Marbles, by Dean Six, Susie Metzler and Michael Johnson?
That has a lot of history in it.
Maybe not the definition of "experimental".
The guy who said experimentals were large marbles was Alan -- they guy with all the Claudias, not Alan Basinet. I don't know the source of his information. It might have been specific to the era in which corkscrews were being made. I don't know.