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Microprinting is one of many anti-counterfeiting techniques used most often on currency and bank checks, as well as various other items of value. Microprinting involves printing very small text, usually too small to read with the naked eye, onto the note or item. Microprint is frequently hidden in an inconspicuous, unnoticeable area on the note or item. For example, on the series 2004 United States $20 bill, microprint is hidden within the border in the lower left corner of the obverse (front) side as well as the Twenty USA background. However, microprint is sometimes placed in a prominent location on the item, and may even be labeled with an MP symbol as a warning that the note or item contains microprinting. On most bank checks in the United States, the line on which the account holder signs his or her name is microprint text, and the microprint line usually includes the MP symbol next to it. An additional safety feature often used is an easily overlooked spelling error inserted somewhere in the microprinted text. For instance, in old Finnish passports, there was a microprinted repeated text Suomi Finland which in one (and only one) instance was intentionally misspelled as Soumi Finland.
Microprinting works as an anti-counterfeiting feature because text of such small size is very difficult to reproduce accurately during attempts to counterfeit the note or item on which it is printed. When the note or item is placed in a photocopier or computer scanner, a line of microprint text may appear to the copier or scanner as a dotted or solid line if the scanning resolution is too low. Likewise, a printer may be incapable of reproducing the microprint, which will then appear in the same manner on the counterfeit note or item when it is printed. Likewise, attempts to counterfeit using a printing press do not accurately reproduce the microprint, because the text is too small to engrave into the printing plates using methods available to the general public . Thus, microprinting, along with other anti-counterfeiting methods used on the note or item, ultimately serves to confirm that the note or item on which it is printed is genuine.