Yes, you can use SAEs and GAEs at face value.
Why couldn't it have been devalued and left in circulation?
How does anyone know if you use it or not? Anyone that matters, that is.
Everything I aquire is private property. How does anyone know what form of "money" I used to aquire said item?
As example, if I mow my neighbors lawn for the agreed upon price of $31.98 {current silver spot} and when I finsh mowing I am offered FRNs worth $31.98 and I take them to the store and trade them for a product I want, how does anyone or anything ever know how I got it or that I didn't use silver money to buy it? They can't prove I used FRNs so it can't be claimed as theirs. {the Feds}
Or conversely, if I am offered an SAE at metal weight value for mowing and I use it to aquire the same item, how does anyone know what I gave for it or that I didn't use FRNs?
Either way there is no record of any of the transactions.
That is the use of the item. Usufruct originates from civil law, where it is a real right of limited duration on the property of another. The holder of an usufruct, known as the usufructuary, has the right to use and enjoy the property, as well as the right to receive profits from the fruits of the property. The English word usufruct derives from the Latin expression usus et fructus, meaning "use and enjoyment", cognate to English "use and fruits".