US Lines 52, International Silver Co. marks


Just wondering if someone can help me decipher the markings on this hot water pitcher. I do know it is made by the international silver co for the United States Lines, I think for the liner USS United States…does the mark US Lines 52 mean 1952 for maiden voyage of the USS United States? Is silver soldering just another name for silver plated (it is pretty heavy but may be from a liner for insulation to contain the hot water)? But, more importantly what does the “I POR Y” mean at the end of the markings? So, here is the full marking:

International Silver co.
Silver Soldered

U.S. Lines 52

Patent 87491

Thank you for your assistance in advance…sorry there is no picture…I am having a problem with my photo editor. Julie