Hi-
While I cannot speak of your specific piece, many newspapers did produce supplements like that, and many of these are not catalogued anywhere. Is this item online or can you hold it in your hands? If it has typical tears, staining, and smell for a 100 plus year old newspaper than chances are it is real. These supplements do not have high value so the chances of reproduction are less (but not nil). Please post scans or a digital picture if you can.
Alan Elefson
aelefson@hotmail.com