US Scott # 1774
Value of this stamp used is minimal, you can purchase it for 15 cents from a dealer, and the cost is mostly to for the overhead associated with it. Mint condition, totally unused with original gum it can be purchased for $1.25. Which means a dealer might give you a quarter for it if they are willing to be bothered with purchasing a single stamp.
US postage stamps do not expire -- they are always worth face value as postage.
"A " stamps are the same as 15-cent stamps.
Flag stamps were 42 cents face value, they were supposed to be forever stamps, postage never to increase from that 42 cents, but that flew out the window real fast.
Face value for postage remains valid until the government de-values them. In the US, stamps issued since 1865 are still valid for postage. The value to a collector varies based on supply and demand.
$12.50
It may have value if you can find someone to buy it from you. A postage stamp has value, but not anything that you can demand. You can't hand one to a clerk in a store and they have to take it.
Ordinary stamps were 3 cents each in 1916 .
The F series stamps were issued in 1991. The postage stamp has a face value of 29 cents.
15 cents.
You can use forever stamps for an ounce of postage forever. They never lose their value for one ounce of postage.
Forever stamps have the value of the current First Class Postage Rate. Currently they cost 49 cents. They can be used 'forever' to mail one ounce of US Postage.
Certainly, that is what they were created for, to serve as postage. Just make sure the total face value of the stamps equals the appropriate rate for the envelope or package.