Hi Shelly,
There are several different catalogs that can be used to identify the USA stamps and they provide the catalog #. The particular catalog and catalog # is usually used to uniquely identify the stamp. In stamp collecting hobby it is also cusomary to identify the country, year of issue, denomination, and description of the stamp being talked about if possible.
For USA stamps I think the Scott catalog is most popular in the USA.
Many libraries carry the Scott catalogs in the reference section.
You can go to Mystic Stamps website and look at their on line catalog - they list their stamps by Scott #.
You can also visit this site
http://album.dweeb.org/Hover your cursor over "Album Pages" shown at the top of the page to see the different year ranges of the stamps he has. Then navigate to the stamp you are looking for. His are also listed by Scott #.
Hope this is helpful.
Kind Regards,
Dave N.
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