(c)Certain residents of possessions considered citizens of the United States. As used in this part, the term "citizen of the United States" includes a person who makes a gift after September 2, 1958 and who, at the time of making the gift, was domiciled in a possession of the United States and was a United States citizen, and who did not acquire his United States citizenship solely by reason of his being a citizen of such possession or by reason of his birth or residence within such possession. The gift of such a person is, therefore, subject to the tax imposed by section 2501 in the same manner in which a gift made by a resident of the United States is subject to the tax. See paragraph (a) of § 25.01 and paragraph (d) of this section for further information relating to the application of the Federal gift tax to gifts made by persons who were residents of possessions of the United States. The application of this paragraph may be illustrated by the following example and the examples set forth in paragraph (d) of this section: Example. A, a citizen of the United States by reason of his birth in the United States at San Francisco, established residence in Puerto Rico and acquired Puerto Rican citizenship. A makes a gift of stock of a Spanish corporation on September 4, 1958, while a citizen and domiciliary of Puerto Rico. A's gift is, by reason of the provisions of section 2501(b) subject to the tax imposed by section 2501 inasmuch as his United States citizenship is based on birth in the United States and is not based solely on being a citizen of a possession or solely on birth or residence in a possession.