It is probably a 40 Lire stamp being from Italy.
Identify the exact stamp using a catalog. This may involve learning about perforations, watermarks and colors as well as condition. The catalog will provide a value. The value is what a collector could expect to pay for a stamp in fine/very fine condition. If selling, most cases you would be lucky to get 75% of the catalog, unless it is very valuable, then an auction would be worth looking into. The most common American catalog for identification is Scott's. Others are Stanley Gibbons, Minkus and even the US Postal Service Catalog of stamps.
According to the website United States Non-denominated Stamp Values, the face value is 37 cents.
Cost of a postage stamp was dependent on the face value of the stamp. The most common rate stamp is for First Class Mail. In the United States 2000 that was 33 cents for the first ounce.
In the United States the first class stamp was 2 cents until July 1932. Then the price went up to 3 cents.
In the United States, in 1921, a first class postage stamp would've cost 2 cents.
Cost of a postage stamp was dependent on the face value of the stamp. The most common rate stamp is for First Class Mail. In the United States in August of 2008 that was 42 cents for the first ounce.
As of August 2021, the cost of a first-class stamp is 58 cents in the United States.
20 cents was the cost of mailing a first class letter back in 1982.
Cost of a postage stamp was dependent on the face value of the stamp. The most common rate stamp is for First Class Mail. In the United States 1922 that was 2 cents for the first ounce.
As 08/21/2012 the butterfly stamp is 65 cents.
Cost of a postage stamp was dependant on the face value of the stamp. The most common rate stamp is for First Class Mail. In the United States 1925 that was 2 cents for the first ounce.
The H stamp is worth 33 cents. Yes, you can add a 1 cent stamp to cover 34 cents worth of postage.
This stamp is called an F makeup. It is worth 4 cents. It was issued in 1991 along with the F stamp which had a value of 29 cents