It depends on a lot of different factors. In addition to knowing what country they are from, what year they are issued and the condition, you have to identify the specific stamp. A catalog on line or in you local library can help you figure out these and find a catalog value.
You can find 1978 Commemorative stamps of America on about.usps.com/who-we-are/postal-history/stamps-postcards.htm
what is the 1981 royal wedding commemorative crown worth
It may be purchased online from StampsForSale which has many commemorative stamps. You may also shop at RoyalMail which has a variety of gifts and stamps.
In general, they will have minimal value. You will need to more clearly identify the stamp to determine the value. There are a number of variations. Consult a stamp catalog to identify it.
I believe it is worth 150,000.
You can find books on Historic stamps of America 1978 Postal commemorative society on en.allexperts.com/q/Stamps-Philately-1610/2009/2/books-stamps-great-grandfather.htm
Face Value
$6.00
Nothing because while it is a commemorative medal it does not seem to commemorate anything.
H. D. S. Haverbeck has written: 'The commemorative stamps of the British Commonwealth' -- subject- s -: Commemorative postage stamps
These are five cent commemorative stamps. They are worth 20 cents used and 35 cents not used.
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