From an essay, "The Traveling Bag" in The Railroad Trainman, April, 1891:

For the benefit of the man who in his youth hadn't pockets enough to hold all his "money, marbles and chalk," I am going to give the result of an actual investigation of one of these [women's] bags, (it happened to be a traveling bag,) and in the future if you hear a woman say, ''small boy's pockets," you will know how to retaliate.

From Slang Fables from Afar by A. L. Kleberg, 1903:

He was this sort of fellow from the time he had pockets in which to rattle money, marbles and chalk, until the sweet End came.

I infer that "money, marbles and chalk" represent the kind of thing small boys are likely to carry in their pockets, and regard as wealth.