Riverton Silver was a division of A.R. Justice of Philadelphia. Although Justice was in operation from 1880 to c1935, the Riverton Division went bust in 1899.
It was common for flatware manufacturers to offer their products engraved (or embossed, if the order was large enough) with the names of hotels, restaurants and other establishments, including ships. I would expect that this relatively small maker would be largely taking such orders from the surrounding localities, so you may just need to look for an establishment with that name (eg Fredonia Hotel or whatever) which was in operation at least sometime between 1880-1899 and not a million miles from Philadelphia. There is a Fredonia village in Pennsylvania as well as the one in NY and they’re both about the same distance from Philadelphia (although not exactly on its doorstep).
There were also many ships with that name, including at least one passenger liner operating out of New York but I didn’t find a likely one within that time frame.
