Complex sentence: In 1891 he returned to St. Petersburg, working exclusively for Fabergé until 1904 from his workshop at 58 Demidov Cross-Street/Ekatarinski Canal.
Split into simpler sentences: In 1891 he moved to St. Petersburg to work exclusively for Fabergé until 1904. His workshop was at 58 Demidov Cross-Street/Ekatarinski Canal.