Hallmark was used by WILLIAM ADAM INC.Birmingham and New York...Bought out later on but began in 1885,There was also an ADIE BROS(THAT USED A MORE SIMILAR MARK BUT THE STYLE IS OF adam).of Birmingham as well started in 1906,Based of style of tea pot I would say you have an earlier(19th.Cen.) William Adam tea pot BUT NOT being an expert this is only my opinion...HAPPY HUNTING ALL!!!