Dating the Casablanca Daybill
I can only ever find this poster referred to as an R40s poster



I believe we can now confidently narrow it down to R49, the first re-release season I have found in Australia started in July of 1949 and ran through to around November that same year in various states. Here's an advert from September that year:

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Comments
Casablanca is obviously Warner Bros.
Also David, interesting in your newspaper ad that the rating is noted as "For General Exhibition" whereas on the poster it's "Not Suitable For Children"...
I have seen it listed as a R46 release. Then again someone found one in a lot of posters under the floor that all dated from 1944-48 so it could very well slot in there somewhere.
Australian Feature Film Poster Printers 1897+ (possibly 1946)
Josef Lebovic (possibly 1947)
Newspaper Clippings
1949:
^ link
1952:
^ link
1953 in a national magazine:
^Page link
Also 1953 (regional newspaper):
^ link
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It does seem like the original release was reused later on at some point in the later 1940s in certain areas with the altered censorship snipe. Perhaps if the supply was low the 2nd release one discussed here noting the Academy Awards was then printed...
Might be my internet connection, which is a little slow.
I've posted it to the facebook page.