Commercial overprint

Commercial overprints, or security overprints, are controls printed on revenue/fiscal stamps, postage stamps used as revenues and even postage stamps. They were/are mostly used on stamps of Great Britain and the Commonwealth. Partly used to prevent theft, they could also be used as a advertising item when used on receipts. Revenue/fiscal usage can be confirmed by pen cancels or blue/purple/violet cancels.

Usages as controls on postage stamps for postal purposes appear to have been limited to a few Victorian and Edwardian era stamps. These should not be confused with overprinted officials.

Obsolete German inflation issues, still plentiful mint today, were overprinted with advertising by various stamp dealers.  File:GB rev with commer ovpt.jpg|Great Britain revenue fiscal stamp used. File:GB Commercial.jpg|Great Britain postage/revenue stamp with message indicating usage on sales receipts. File:Hong Kong DP ovpt.jpg|Hong Kong, Daily Press control overprint. File:Transvaal CSAR ovpt.jpg|Transvaal, Central South African Railways control overprint. While this type is a control overprint, a stencil outline overprint version or perfins are official stamps. 

The Commercial Overprint Society of Great Britain not only has an online key to identify abbreviated British commercial overprints, but also lists countries using commercial overprints. See: the society's website

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