If I knew about this one before, I forgot about it.
STANDARD TOY MARBLE COMPANY, THE: proper name. (1894-1922) Akron, Ohio. Owned and operated by Frank J. Brown and family, manufacturers of ceramic marbles; commies, crockies, Jaspers. Believed to be the first to manufacture and market marbles for industrial purposes, largely as inert, filtration objects for municipal water systems; manufactured ceramic marbles as large as 5 inches in diameter, likely as pump value balls.
http://www.americantoymarbles.com/glossary.htm
The largest in this group is about 1 and 5/8".
The second grouping has 1 and 1/2" marbles.