SOLVED
I recently came across this video on YouTube, which shows a 8/12 port, WW2 siren made by Klaxon.
https://www.youtube.com/watch?v=F8ZomBysu20
Whilst the model name is not known yet (I asked in the comments), this matches up very very closely with the siren at Port Stanvac. Too, whilst we don't have a confirmed location, further evidence of this being the model is provided by a worker recounting seeing a Klaxon branded siren controller when the site and siren were still operational.
Klaxon has been a big siren distributor / seller in Australia for many many years, which is why I draw the conclusion of this being the model used at Port Stanvac.