W.F.J. Hana, Nederlandse Klokken, Haarlem, 1980, p.174
Johan Bernardus Vrythoff (Frijthoff) is recorded working from c.1750-c.1795. He was chairman and dean of the Clockmakers' Guild in The Hague 1773-1797. In 1764 he is known to have bought a house on the south side of Herderinneweg or t'Zand.
An enamel dial table clock with moonphase and alarm, but in a japanned case, by Johan Bernardus Vrythoff was sold Christie's New York, the Property of Halstead B. Vander Poel, Important English Furniture Including the Paley Collection, 14 October 2004, lot 240.