Duke asks what the silver box was made to hold, "snuff, cuff links, Colonial condoms". There actually were condoms in the 1700s. Granted, they were made from chemically treated linen, or sheep intestines, or animal bladders, or even hand stitched fine leather. They were used to prevent STIs as well as to prevent pregnancy.
Duke mentions he won his boat from Ray Fiegler up in Castle Rock. Ray Fiegler is a known alias of Randall Flagg, a common King villain.