By the 1890s they also had a large factory and office located in Montreal. The parentcompany was part of a number of related companies amalgamated into the International Silver Company in 1898 and that company continued through the 20th century, thrived during WW2 in war contracts and became Insilco in the 1960s. Under new management the company was diversifying into other fields and closed the silver business on March 20 1981. Insilco did not thrive, it too closed in 1991.
Though the products and history of the main US company is documented online, the details and fate of the Montreal operation doesn't seem to be and I cannot find evidence of its existence by the 1950s.
Lots of information online on the company and its line of products, Catalogs and hstory here