They are Arab coins.
Might have been taken when Saladin was defeated there by Richard I. Richard commanded both the Hospitallers and the Templars as well as his own guard.
Nights Hospitallers controlled that castle from 1261-1265 (when it fell).
Last Christian holding to fall to the Muslims was Acre. (Templars were last to leave in 1291, those that did not fight to the death.)
How can you tell that? The story didn't say, either way.