I think the mark is H. S. Co and that one need look no further than the Silverplate Marks section of this site to make a positive identification:
http://www.925-1000.com/silverplate_H.htmlHartford Sterling Company used different marks, sometimes merely these initials and sometimes also incorporating a faux coat-of-arms.
Despite the company's name, the piece in question is not sterling, of course.
It looks to me like a purely decorative piece or perhaps a vase. It probably was one of a pair, which would be perfect on the ends of a mantle or sideboard. Most likely dates to the 1920s-1930s, as the OP states.
Regards,
DR