While the initial assumption would be an item referred to as silk would be made of silk yarns this is not necessarly the case. Referred to as "Satin" on the ad backs of the S74-1 silks this was a reference to the shiny smooth finish. In the early 1900’s, weaves referred to as satin often were made of silk or a combination of silk and a cheaper yarn, most likely cotton. Under magnification a single yarn from an s74 appears to be twisted, which could mean a silk/cotton blend, 100% satin silk, or 100% satin cotton. Theses were the predominant fabrics available in 1911. Without forensic testing there is no way to know for sure, but we believe that the silks were woven from either pure silk or a combination of silk and cotton.
It is likely that American Tobacco had the silks printed with the brand advertising and factory designation and then distributed to the various factories to be folded and inserted into the cigarette packs.