are treasury dollars. But, they, when due, are paid with Federal Reserve Notes (no backing by taxes, etc.). Federal Reserve Notes are backed by bank deposits. Treasury (Red Seal) Notes are backed by the US Treasury (as well as coins).
The Fed disperses coins to banks but it does not own the asset.
There is risk in FRS notes that the UST notes and coins do not have.
This is the most important thing. If you can see this, it is a marker of which ways to go.
I think.