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Coding Documents by Trace Element Inclusion

IP.com Disclosure Number: IPCOM000090332D
Original Publication Date: 1969-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Tracy, JF: AUTHOR

Abstract

Documents are coded by inclusion of elements in trace amounts that enable identification as to originating location, date of manufacture, etc. These trace amounts are added to the base stock, printing ink, tinting or other component of the document in different ways.

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Coding Documents by Trace Element Inclusion

Documents are coded by inclusion of elements in trace amounts that enable identification as to originating location, date of manufacture, etc. These trace amounts are added to the base stock, printing ink, tinting or other component of the document in different ways.

Trace amounts of precious metal or rare earth salts can be added that are not common to the process or product being coded. These salts can be used singularly or in combination. Concentrations or combinations can be modified from time to time to denote the time of manufacture, e.g., to date-code the document. Ten parts per million, 10 ppm, of a cobalt salt are equivalent to the year 1968 while 10 ppm of niobate correspond to the eighth month. Care is taken in selecting salts and regulating concentration to avoid health or safety hazards in handling the document, i.e., avoid salts of mercury, lead and arsenic.

Radioactive trace materials with a low level of radioactivity to avoid health hazard can be added. Their presence can usually be detected by instrumentation though final concentration may have to be determined by wet analysis. Material with a known rate of radioactive decay can be used, e.g., carbon fourteen Cl4. Numerous compounds have relatively short half-lives for their radioactivity. By comparing a base measurement at the time the compound is included in the document with that at some later date, the age or equivalent date of manufacture of the do...