Interesting. Seems like maybe it could be some sort of nationally cased watch I haven't seen before. Where is Hobart?
I think I have a similar ribbed case somewhere, I'll see if I can find it.
As Dan mentioned, I think they are SS cases done by Handley in Melbourne.
Coincidentally, my Darlin' was in the city today and her tram ride took her past the site of the old Handley factory, I think it's an apartment complex now.
The Handley factory in 1953.
The Handley factory today.