The 1792 coinage act defined a dollar as .77 ounces if silver. That is why Morgan dollars where .77 ounces of silver. It has never been repealed to my knowledge. http://www.constitution.org/uslaw/coi...
The older dollars had this printed on the front: "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"
Now they only say: "This note is legal tender for all debts public and private"
Legal tender does NOT make it "lawful money" A dollar "bill" or reserve "note" is just an elaborate IOU and a legal contract which they do not seem to want to honor.
The FRN is a contract between the people and the Federal Reserve Bank which they seem to be refusing to honor.
We are trying to redeem this 100 note at the Treasury and we will let you know what happens.