Based on the description, I am quite sure that the mark is actually "QB" with a pansy and fleur-de-lys above: the mark of Quentin Bachelet.
Quentin Louis Bachelet
Born: ca. 1790, son of Marie Louis Bachelet & Marie Josephe Seraphine Goddard
Married: 3 Dec 1816, Paris, St. Paul parish, Adelaide LeProust
Died: 16 Jun 1865, Paris
He registered his mark ca. 1815-1816 at 13 cour de Harlay as a largeworker and successor to Philippe-Jean-Baptiste Huguet. In 1823 he moved to 58 quai des Orfevres, at which address would be best known. He retired in 1844, succeeded by his son Louis Charles Bachelet (1817-1880), who was in turn succeeded in 1877 by his son George Bachelet (1845-1930), all at the quai des Orfevres address.
Ref: Arminjon I, no. 3109 (Note: Although Arminjon spells the name "Baschelet", it is spelled "Bachelet" in literally every other record I have found, including all directory listings and birth, marriage and death records.)