From: thug@phantom.com (Murdering Thug)
Date: Fri, 30 Jul 93 13:47:31 PDT
To: davros@ecst.csuchico.edu (Tyler Yip - UnixWeenie)
Subject: Re: money tracing
In-Reply-To: <9307302002.AA19091@hairball.ecst.csuchico.edu>
Message-ID: <m0oM1Ot-0009FYC@mindvox.phantom.com>
MIME-Version: 1.0
Content-Type: text


Typer Yip writes:

> since 1990, the Treasury has placed a nylon strip inside the paper of most of
> the printed money ($10's and above, I believe).  This strip has letters on it,
> spelling out "USA TWENTY" (for the $20 bill) such that it can only be seen if
> light is passed through the note.  This was officially meant to prevent the
> high quality scanners and color printers from being able to forge money, since
> the scanner would not be able to reproduce the reflectively-invisible letters
> in the strip.
> 
> Wonder if they could include such a technique in money tracking.
> Has anyone ever checked the green ink on money for magnetic resonance?

The black ink that is used to print the front side of U.S. cash contains a
very finely ground black iron oxide powder.  The ink is magnetic.  This
magnetism is used mostly by vending & change machines to distinguish real
bills from forgeries/photocopies.

A vending machine that accepts paper money typically has three tests for
cash validity.

          1. A digital image scan and imagage signature comparison.
             This test also determines the denomination of the bill.
             (good photocopies of bills can get past this test)
     
          2. Ultraviolet light test.  Real bills (printed on non-chemically
             treated paper) do not glow.  Most other papers, especially
             chemically whitened papers do glow, and are flagged as fakes.

          3. Magnetic ink detection.  Real bills are printed with magnetic
             ink, forgeries/photocopies are not.


Thug