This is the signature of Moses Gaster (1856-1939), who served as the hakham (rabbi) of the Spanish and Portuguese community in London. Gaster was ordained as a rabbi at the Jewish Theological Seminary in Breslau and received his doctorate from the University of Leipzig.
Gaster was an outspoken advocate for the emancipation of Romanian Jews, which ultimately led to his banishment from Romania in 1885. After his expulsion he moved to London and there was appointed hakham of the Sephardic community in 1887.
Gaster was also an active Zionist; the first draft of the Balfour Declaration was written at his home. He was a prolific writer and focused much of his research on Romanian and Jewish folk literature.