"THE GOLDEN FROG"
Simon Templar flew into San Carlos in South America at the beginning of this adventure - but was he flying in to a country by that name, or some country's capital city sporting that name?
In the beginning of the episode, various characters spoke of San Carlos as though they were talking of a city. Even though I never trust on-screen graphics, the usual establishing shot for this episode only showed an aerial view and read: "SOUTH AMERICA".
But at the end of the episode, Alice Nestor told Templar that she and her father had sold the guns to the government of San Carlos, which implies that San Carlos is a nation.
So here's the easy splainin. Simon Templar was in San Carlos, San Carlos. La ciudad tan agradable que lo nombró dos veces.
(Although when he arrived, he might have thought he was in Haiti if he looked out the window as the plane landed. The San Carlos airport looks just like the Haitian one in the episode "Sibao". They must have been designed by the same architect....)