The Omani Shamshiir.

[Excalibur2025]

Here's a picture of the last indigenous king of Zanzibar (who reigned in the 15th century), with what appears to be a shamshir.

This could indicate that the shamshir was a badge of office for Zanzibari rulers, or a Victorian era (?) Orientalist illustrator retroactively inventing a tradition.

It is worth noting that indigenous Zanzibaris call themselves Shirazi and believe they are descended from Persians. There is not much left of this influence in the modern era except that a version of "Nowruz" - the Persian New Year - is celebrated on the south east tip of the island.