Post any photos of the poster once you receive it. It might have a more distinct smell, as you say, but it might also hardly have a smell. I believe it will depend on how well the object was stored- the severity of decay of the lignin in the paper. Only a small portion of my photos have much of a smell including the ones that are over a hundred years old now. If you have enough magnification it should look something like what is below.
The ultraviolet light only tests for the presence of optical brighteners. The paper will glow if it has optical brighteners, or various sized dots may appear from when the paper was in contact with specific chemical compounds. Treated fakes and those printed on period paper can and will show up as false negatives.
The difference between period and non-period paper should be readily apparent. It is hard to get a picture of but very easy to see in person. Here are two original photographs on the bottom compared to modern printer paper and a repro photo printed on modern paper.
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