1909
Martin Christensen advocating for increased tariffs to protect the infant American glass marble and caster ball industry. E. Strobel arguing against.
Tariff Hearings Before the Committee on Ways and Means of the House of Representatives, Sixtieth Congress, 1908-1909, Vol. VIII, pp. 7881 - 7883
1913
Tariffs again. Martin Christensen contributes information.
62nd Congress, 3rd Session, December 2, 1912 - March 4, 1913, House Documents, Vol. 131, pp. 5205 - 5230
1917
This might be a reference to MFC. It's some company which makes marbles and caster balls, and exports some of their product.
The Glass Industry: Report on the cost of production of glass in the United States, p. 392
There are other marbles references on other pages.