Mombasa was part of the state of Zanzibar until 12 December 1963 when it was ceded to be incorporated into the newly independent state of Kenya.
Fake
Actually the reference to Kenya is on the 1964 certificate letterhead.
At the time the document was prepared, Mombasa was indeed Kenya.
Not fake. :)
Fake
Portugals reign over Mombasa lasted for approximately 200 years, after which they were overthrown by the Omani Arabs, who themselves would be forced to give up Mombasa to its final captors: the British. The British took control of Mombasa in 1895, after the sultan of Zanzibar leased the town to the British. The British East African Protectorate was established, and promoted European colonization of Kenya lands and resources. The British took strides to establish control of the strategically important port, and completed a railway line in the early 1900s from Mombasa to Uganda.
Source: Mombasainfo.com
Founded by Arab traders in the 11th century, Mombasa was an important port for trade across the Indian Ocean. It was visited in 1331 by the Arab traveler Ibn Baṭṭūṭah and in 1498 by the Portuguese navigator Vasco da Gama. Because of its strategic position, it was continually fought over, passing among the Arabs, Persians, Portuguese, and Turks until 1840, when the sultan of Zanzibar finally gained control. It came under British administration in 1895 and was capital of the East Africa Protectorate until 1907. Mombasa became a municipality in 1928 and assumed council status in 1959.
Source: Encyclopedia Britanica
Is somebody using Wikipedia as a reference again?