The Small Size 500 dollars United States Notes were first issued as series of 1928, last as series of 1934-C. A major change between series 1928 and the 1934 series, is that the 1928 series had a redemption clause that said:
"Redeemable in gold on demand at The United States Treasury or in gold or lawful money at any Federal Reserve Bank."

while the later notes said:
"This note is legal tender for all debts, public and private, and is redeemable in lawful money at the United States Treasury or at any Federal Reserve Bank".