Busselton Historicial Society have a Timber rudder in thier collection for a Boat that was owned by the Camillieri Family. View it here: Registration Number.
The contextual information given is that "Douglas Camilleri was the son of Frederick William Ponsonby Cammilleri."
This makes me think that maybe it was Douglas's boat? Was it a commerical boat or a recreational boat? There are so many questions raised for me by this random rudder! What was the connection to St Davitts where he grew up.