Am I missing something or does the author not explain why bring back specifically the $500 bill? The defense seems to be, "Well, in case of catastrophe, we should have cash," which I agree with, but that still doesn't explain why the $500 note. If anything, the author makes a good case for maintaining smaller denominations.
The $500 bill pictured in the article is a gold certificate: "Redeemable In Gold On Demand at the United States Treasury"... Looks like all $500 gold certificates were printed in 1928, as the 1934 high-denomination bills were only used for intra-federal reserve transfers:
