"Ordinary Old" wood as far as I know. Dunno actually. It would be some sort of local timber they were made out of.
If you have a close weeny microscopic look at my dogboxes on Garahbara, you will see they are decaled/numbered exactly the same as your fav "street scene" pic. That is the same pic I used to decal and number the model kit.
The two tall brown buildings in the background of the red "Tait" with the banner on the front have since been demolished. They won an achitectural award in the 60's for inovative design, and featured on the phone book covers of their day.
The Premier of Victoria won an election with the policy of demolishing them, as they had become a city "eyesore" since they were built.