The B stamp is worth a face value of 18 cents. There have been several non-denominated flag stamps. They were used to cover increases in postal rates when they weren't sure how much would be authorized. Check the US Postal web site for specific pictures to match up with the one you have.
15 cents
That stamp was issued in 1985. It has a face value of 22 cents.
Forever
The current value for a standard postage stamp is 46 cents.
The F series stamps were issued in 1991. The postage stamp has a face value of 29 cents.
Face value of the original stamp was $0.20
The stamp-postage value of a stamp is visible on the front of the stamp.
The B stamp pictures a stylized eagle. It has a value of 18 cents. You can still use it for 18 cents worth of postage.
The face value of the D stamp was 22 cents when issued in 1985.
96214455 doollars
15 cents.
The value of an extra postage stamp is typically the cost of the stamp itself, which may vary depending on the denomination printed on it. It can cover the postage for an additional letter or package, or it serves as a backup in case the original postage is insufficient. Ultimately, its value lies in its utility for mailing purposes rather than any collectible worth, unless it is a rare or unique stamp.