This is very interesting. I have seen a similar engine fitted to a 1916 machine here in Sydney (Randwick is in Sydney for those unaware - and was where the Royal Australian Navy - RAN - supply depot was) - minus the stationary engine oil sump etc. I spoke to the previous owner of this machine, and he told me that he had found that that these engines were used as generators to power electric wireless sets. Fascinating to see another one turn up!
Cheers, Graeme