Have you applied for a patent for the black penny stamp?

The so-called "black penny stamp" has not been patented. I wonder if the following patent has anything to do with what you said:

Date of application: May 7, 2002.

Name: Method and system suitable for confirming safety signs.

Rights: 200 1.5. 10 USA 60/289977; Usa 10

Applicant: Pitney Baosi Co., Ltd.

Address: Connecticut, USA

abstract

A method and system suitable for confirming articles through safety signs. The safety sign provided by this project is the use of an OVD ink, which can absorb light within the visible wavelength range to produce visual black and generate red fluorescence emission under the excitation of ultraviolet light. Under the irradiation of visible light and ultraviolet light, an image scanner can be used to obtain visible light images and images from safety signs. Compare these images and find out the basic match between them. Safety signs can be postmarks, barcodes, symbols, messages and images of stamps. The items to be confirmed can be emails, checks, labels, bills, documents, ID cards, etc.