Links to links that Kenya did not call itself a Republic until after December 12, 1964...
However we have now learned that the Coast Province declared its own independence in October of 1963, announced that it would join Kenya, and referred to Kenya as "The Republic of Kenya". Perhaps it was wishful thinking on the Coast Province leadership, but since Mombasa was part of the Coast Province that was officially referring to itself as "The Republic of Kenya," after October 1963, it stands to reason that official documents of that region, including Certified Copies of the Registration of Birth, would include that title.