Lauser was a German citizen who settled in London. In 1881 he was living at 12 Maitland Park Villa with his wife Cecilia (b. ca 1851), two sons, Gustav (b. ca 1864, who became a printsellers assistant), and Charles (b. ca 1876), and another German born printseller, Adolf Rosh or Roth. By 1901 the Lausers were living in Hampstead.
Gustav Lauser was a print dealer who knew Whistler from the late 1880s. He bought and sold Whistler's prints, often in collaboration with Edward G. Kennedy of Wunderlich and Co., New York (#07216 #07184).
UK census 1881, from http://www.familysearch.org (accessed 2004); UK census 1891, 1901.