The Omani Shamshiir.

[Jim McDougall]

As well noted by Kahnjar, Zanzibar was a key trade center in the 19th century and of course being an Omani sultanate, there were considerable numbers of the types of edged weapons commonly in use in Arabia in that context.

The Persian shamshir was a highly prized sword by Arabs throughout the Dar al Islam, so presence of this example in Zanzibar is not unusual. It seems unusual that the hilt material is gone as I thought bone, ivory etc. would survive in an archaeological deposit. More likely of course the ivory would have been taken for its value and the sword discarded.
By the same token, if the hilt was silver, that too would have been taken.

Always fascinating when any weapon is found in situ, and speculating how, when and why it ended up where found. Thank you for posting this!