Oststraße 4, Grenzhausen Hesse-Nassau, Prussia, from 1904 until 1938. In 1939, Oststraße 4, was renamed Auf der Heide 32, Höhr-Grenzhausen.
The address has now be renamed Töpferstraße 34, Höhr-Grenzhausen, Rhineland Palatinate.
(N.B. The towns of Höhr & Grenzhausen merged on the 1st April 1936. The federal state of Rhineland Palatinate was established on the 30th August 1946.)
Steinzeugwarenfabrik / Stoneware manufacturer
Known dates: Founded circa 1865, Peter Hammer died in 1878 so his widow ran the company as Peter Hammer Witwe, until circa 1922, when their son Simon Peter, (born 1872) took over. The company continued until 1953 when Simon Peter died. The majority of their product range was mainly tableware bottles. Simon Peter's son Egon continued to use the workshop until the 1970's, in spite of a major kiln fire in 1968.
Reference: Coblenz Adressbuch
The Peter Hammer Witwe mark anecdotally looks like this, i.e. a Dr Fritz Hammerschmidt mark reversed. The author has never yet seen this mark, or a stein which can be proved to have been made by Peter Hammer. 
An advertisement from Führer durch Höhr, dated 1907 