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.