However, when I can't find a book, I've been carrying out a manual search of both the British Library and National Library of Scotland catalogues, and then creating a manual entry based on their data and noting the data sources used in the comments section.
Ideally I'd simply rerun the Overcat search from Library Thing against the British Library, but LibraryThing's link to the British Library catalogue is unreliable, so searching manually it is for the moment.
Given that I would guess that around 90% of the pre 1950's items in the collection were sourced from the UK, even though the book in question may have originally been published in the USA, so far there's no need to check the Library of Congress, or any of the local state libraries, to track down a cataloguing record.
However, working with the books directly has benefits - for instance the Treloar's hygenic library label at the top of this article came from a 1930s edition of a Max Brand Western novel, suggesting that perhaps the sometimes buying books second hand to add to their collection.
It also suggests that circulating libraries were still a thing in early 1930s Australia - post depression money was tight and being imported, books were relatively expensive. (Hygenic libraries were circulating libraries that made a point of sterlising books between loans, either by spraying them with antiseptic or placing them in an oven.)
One might have expected that public libraries might have taken up the slack, but perhaps it was the case that commercial circulating libraries provided a better choice of popular fiction. (I don't know enough about public libraries in 1930s Australia, I'm waving my hands here).
Also, sometimes on gets to touch history - in our collection we have an 1863 edition of Alice King's now forgotten three volume novel Eveline.
Forgotten now, but obviously very popular when it first appeared as the flyleaves of each volume - volume 1 is unfortunately missing - are endorsed 10 days allowed in ink
suggesting that there was considerable demand, and that patrons could only sign the book out for 10 days rather than the more normal fourteen or twenty one days.

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