AU prefix seems only for Waratahs, so seems more than co-incidence.
Other end of the alphabet though.
D33 here knows more about serial numbers, may be able to advise.
Lot of chat a while back here about these models being a variety of Excelsior, from UK - so in the right section. !!
Whether they were imported whole, or built up from some sort of kit is an interesting question.
A few varieties of other brands were quite similar, but different in minor details..
Look forward to a pic or 2 ?