letters paten

from Bouvier's Law Dictionary, Revised 6th Ed (1856)
LETTERS PATENT. The name of an instrument granted by the government to 
convey a right to the patentee; as, a patent for a tract of land; or to 
secure to him a right which he already possesses, as a patent for a new 
invention or discovery; Letters patent are a matter of record. They are so 
called because they are not sealed up, but are granted open. Vide Patent. 
    

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