Additions_to_US_Catalogs
What should be listed in a catalog?

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19th Century US Stamped Envelope Catalog Corrections:

20th and 21st Century US Stamped Envelope Catalog updates/corrections:
20th and 21st Century US Stamped Envelope Catalog supplemental information: Some additions to the United States Multiple Advertising and Discount Postal Cards: Stamped Envelope and Wrapper Specimens of the United States