I also believe it is silver plated/nickel silver, e.g. 80 gram used on 12 spoons. The teapot mark leads my taught to Norway. In Oslo was a silversmith by the name of Johan Ludvig Sæther, active 1924-1963. His mark was a teapot, but on silver. Is it him or not is difficult to say because here we have a plated object. Marks on silver plate can be anything. There is no standard whatsoever.