Scott # 999 is green and shows Carson Valley, value is $.04.
3 cents
three cents
Worth 6 cents
The lowest value US stamp was the 1/2 cent. A couple different versions were issued.
8 cents.
A 28 cent stamp that is unused can always be used as 28 cents worth of postage. If it is used, it probably has a minimal purchase price of fifteen cents from a dealer.
No, it is only worth 32 cents.
I bought one for about 20 cents.
4 cents.
3 cents
Air mail stamps are good for ordinary postage- your stamp is still worth 7 cents if unused.
That is Scott number US 2418 It has a value of 1.30 mint and minimal 15 cent used.
Not sure what you define as an original stamp. A US 3 cent unused stamp is worth 3 cents toward postage. It may have more value as a collectible, but you would have to consult a stamp catalog to fully identify it and get an estimated value. You might try the online version at Mystic Stamps as a starting point.