Well they are "Federal Reserve Notes". That is the first key. Another key is that checks printed by check printers do not make reference to lawful money however the "$" is allegedly a symbol for lawful money. What may also cause problems is that clearinghouse certificates could be under the National Banking Act be 'deemed' to be lawful money under certain circumstances (for certain reserve purposes?) and it might be so today and that might give rise to a kind of double talk. And that might explain why you could give a bank a PN in lawful money and they cut you a check in clearinghouse points.
I'd tend to say that the primary lawful money in circulation today in the United States of America are negotiable promissory notes denominated in "lawful money" and corporate bonds denominated in lawful money and their electronic equivalents. If checks are lawful money then checks, money orders and the like would be such--in any case it is likely that they make up the currency.
As for "Father's trustee"... have you ever considered the role that any of the following play in the monetary system or what their duties are and how they might relate to your prosperity:
[*] Secretary of United States Department of the Treasury
[*] any municipal, circuit or district court clerk
[*] the commissioner of Social Security
[*] the secretary of state of each U.S. state, district or territory
[*] any city or county clerk (not necessarily court clerks)
[*] the chief counsel or president of any state bank or U.S. bank.
IMHO, fixation on printed notes these days is a colorful distraction. Much is done via book entry and by transfers made electronically.