from The Secrets of Oz that you linked above:

The yellow brick road (the gold standard), the emerald city of Oz (greenback money), even Dorothy's silver slippers (changed to ruby slippers for the movie version) were powerful symbols of author L. Frank Baum's belief that the people - not the big banks -- should control the quantity of a nation's money. Debt free money.

Bill Still's earlier documentary The Money Masters, is a longer version of the above, also worth watching.

Bill Still made a documentary on this: The Secrets of Oz

The yellow brick road (the gold standard), the emerald city of Oz (greenback money), even Dorothy's silver slippers (changed to ruby slippers for the movie version) were powerful symbols of author L. Frank Baum's belief that the people - not the big banks -- should control the quantity of a nation's money. Debt free money.