Although these labels are called by several names, for the sake of simplicity "test stamp" will be used in this article. It is the name used in the Scott Specialized Catalogue of United States Stamps and Covers.
The Scott catalog lists U.S. test stamps that were used to test coil and booklets vending machine formats, offset printing, perforations, paper, gum and a host of other innovations. According to the introductory paragraph in the Scott catalog's test stamp listing, U.S. test stamps were used for testing of production equipment and stamp vending and affixing equipment by commercial entities and the U.S. Postal Service.
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Guessing the Scott Catalog would help
