X-Patent
On July 31, 1790 inventor Samuel Hopkins of Pittsford, Vermont became the first person to be issued a patent in the United States. His patented invention was an improvement in the "making of Pot Ash by a new apparatus & process." The earliest patent law required that a working model of each invention be produced in miniature.
Elisha Gray
Although Gray had abandoned his caveat, Gray applied for a patent for the same invention in late 1877. This put him in a second interference with Bell's patents. The Patent Office determined, "while Gray was undoubtedly the first to conceive of and disclose the [variable resistance] invention, as in his caveat of February 14, 1876, his failure to take any action amounting to completion until others had demonstrated the utility of the invention deprives him of the right to have it considered." Gray challenged Bell's patent anyway, and after two years of litigation, Bell was awarded rights to the invention, and as a result, Bell is credited as the inventor.