You will need to consult the catalogs. Most libraries will have a copy of Scott's Postage Stamp Catalog of the World. First of all, you have to identify the specific stamp or card. That in itself can be a daunting task, but most of the catalogs are well illustrated with lots of information. Once you know what item you have, the catalog will provide a set of prices that can be used to estimate value.
The best source would be an adult stamp collector that you know to be trustworthy.
If there is a local stamp club, you would find many people who would help you.
If you have a local dealer, he can tell what your stamps are worth to him -- around 10-20% retail if they are stamps that he does not already have too many of .
You can go to your local libraries and look for Scott's Standard Postage Stamp catalog in the reference section.
You can go to the internet and Google "postage stamp values" and find many auction sites, offers from dealers
for free catalogs and people who will appraise your stamps for a few.
You can go to auction sites, eBay being the largest, and see what various stamps sold for in the past.
{| |- | That is pretty difficult. You can visit various stamp dealer sites online and may be able to identify it that way. Visiting a dealer is another option. You can also look for stamp clubs in your area, they may be able to help you. |}
Consult a stamp catalog. It will help you identify the stamp and the information about it. In addition to the year(s) of issue, it can also provide estimated values and other pertinent information.
You can find 1978 Commemorative stamps of America on about.usps.com/who-we-are/postal-history/stamps-postcards.htm
Stamps typicall see an increase in value after the 1st year on the market. This does vary depending on the stamp.
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
In order to give an estimated value it is necessary to know which coins and stamps are in the collection.
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.
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.
The best place to go is just the USPS website. They're the ones that issue all the commemorative stamps and things like that. I'd start there.
These stamps are still good for postage. They are still worth face value to anyone who needs stamps for postage. A dealer might charge twice face for them, so if you could find a collector who was thinking about buying them from a dealer, you could make a deal. A dealer will not likely pay more than face for them.
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.
The ones purchased from the US Postal Service include the stamps.
An easy way to find good value for your stamps is to buy a stamp magazine. Linn's is a good one.