"11 OZ" mark of Samuel Kirk & Son

Some S. Kirk & Son antique silver pieces bear "11 OZ" mark and for someone who is not an antique silver expert it may appear to be the volume of the piece.

In reality "11 OZ" is the silver content mark! The butter dish whose mark is shown on the picture was made by Kirk & Son between 1880 - 1890: one of the two periods when the company used "11 OZ" mark. The first one was 1846 - 1868:

http://www.thestieffcompany.com/The_Stieff_Company/S._Kirk_%26_Son.html

Please also see
http://www.thestieffcompany.com/The_Stieff_Company/The_Story_of_the_House_of_Kirk.html

and search for "11 OZ" in the page. It says

"11 OZ is 11 out of 12 ounces TROY. 11 OZ is 91.66 pure vs 92.5 for Sterling Silver."