I do not believe the maker was Gustav Fredrik Hellstrømk as GH is not the registered mark for G. Hellstrøm & Co . It may have been his father Gustav Wilhelm Hellstrøm from Stavanger. I do not have enough history about the father as GFH changed the name of the company to G. Hellstrøm & Co in round 1902. There is a Danish Maker with the mark GH who you may want to check into.