Posted By:
T206Collector...about the name of the set being called Set #521 (though Burdick referenced at the time that only "several hundred" were known. And the gold border set was known as #520, and it doesn't have 520 cards in it.
All of this is from the following article, which is long but fascinating:
http://www.oldbaseball.com/refs/1930s.htm
Still, I thought it sort of poetic that it was listed as Set #521.