My reference to 628 should have been to 630.
I also notice that the 1948 South Australian certificate does not, as far as I can see from # 620, have “South Australia Government Printer” at the bottom, but it’s hard to tell. Perhaps RubyR can clarify.
I found the document through a google image search. I put in “birth cert” adelaide and it came up on the first page. I don’t know anything more about it.